Aqueous dispersion forming conductive layer, conductive layer, electronic compent, circuit board and method for manufacturing the same, and multilayer wiring board and method for manufacturing the same

ABSTRACT

An aqueous dispersion of the invention has conductive microparticles and organic particles dispersed in an aqueous medium and can form a conductive layer of a volume resistivity of for example 10 −4  Ω·cm or less by electrodeposition. A circuit board of the invention is equipped in an insulating layer and a conducting layer, which includes conducting through parts that pass through the insulating layer, and is favorably manufactured by the invention s method that includes an electrodeposition using an aqueous dispersion of the invention as a electrodeposition solution and using the conductive foil as one of the electrodes after closing the openings at one end of the through holes formed on the insulating layer by means of a conductive foil. A multilayer wiring board of the invention is equipped in a core wiring substrate, having substrate wiring layers that are mutually connected electrically formed on both surfaces of an insulating substrate, an insulating layer that is laminated onto at least one of the surfaces of the core wiring substrate, a wiring layer that is formed on the insulating layer, and interlayer shorting parts that pass through the insulating layer and electrically connect the wiring layer to the abovementioned substrate wiring layer. These interlayer shorting parts are comprised of conductors formed by electrodeposition using an aqueous dispersion of the invention as an electrodeposition solution. Since the conductive layer or the conductor is formed by electrodeposition, the productivity is good and the connection reliability is high.

FIELD OF THE ART

The invention concerns an aqueous dispersion forming conductive layer, aconductive layer formed from the aqueous dispersion, an electronic partequipped with the conductive layer, a circuit board, equipped with aconductive layer formed with the abovementioned aqueous dispersionforming conductive layer, and a method of manufacturing the circuitboard, and a multilayer wiring board and a method of manufacturing themultilayer wiring board.

BACKGROUND ART

Since priorly, the metal plating method has been used to form aconductive layer, which is to serve as an electrode, wiring pattern andthe like on a substrate. Another method of forming the conductive layeris the method of dispersing a conductive powder in a liquidthermosetting resin material to form a conductive paste and applying theconductive paste onto a substrate by coating, printing, or other method,and thereafter thermosetting the resin. Also, Japanese Unexamined PatentPublication No. Hei-9-134891 discloses a thin film forming method,wherein an ultrafine metal particle dispersive solution, prepared byuniformly dispersing ultrafine particles of a metal in an organicdispersion medium, is coated onto a semiconductor substrate and then theorganic solvent is eliminated and the ultrafine metal particles arefused by heat.

Also in recent years, in accompaniment with demands for advancedfunctions and compact size in electronic equipment, electronic parts ofhigh degrees of integration and large numbers of electrodes are comingto be used and the mounting of such electronic parts at high density isbeing required. Thus in place of single-sided printed wiring boards,with which a wiring layer is formed on just one surface of an insulatingsubstrate, and double-sided printed wiring boards, with which wiringlayers are formed on both surfaces of a substrate, multilayer printedwiring boards, with which insulating layers and wiring layers arelayered in an alternating manner on one surface or both surfaces of asubstrate, are coming to be used as wiring boards for electronic partsand wiring boards for mounting electronic parts.

Conventionally, the mainstream method of manufacturing a multilayerprinted circuit board was the method of laminating a plurality of corewiring substrates, each of which is arranged by forming wiring layersthat are electrically connected to each other on both surfaces of aninsulating layer, and thermosetting resin prepreg sheets in analternating manner and performing heat pressing to integrally laminatethe plurality of core wiring boards with insulating layers interposed(this method shall be referred to hereinafter as the “lamination pressmethod”).

However, with this lamination press method, interlayer shorting parts(buried vias and blind vias), which extend in the thickness directionthrough just an insulating layer that exists between wiring layers ofadjacent core wiring substrates, cannot be formed for electricalconnection between the wiring layers, and since interlayer shortingparts (through holes) that extend in the thickness direction through theentire multilayer wiring board must thus be formed, the forming ofhigh-density wiring layers was difficult.

For this reason, the build-up method, with which an insulating layer anda wiring layer are formed successively one layer at a time on a corewiring substrate, has come to be noted recently as a method ofmanufacturing multilayer printed wiring boards with high-density wiringlayers. With the build-up method, high-density wiring layers can beformed since the electrical connection between respective wiring layerscan be realized through shorting parts that extend in the thicknessdirection through just an insulating layer that exists between thewiring layers.

To be more specific, with the build-up method, an insulating layer,having through holes that correspond to the interlayer shorting parts(vias) that are to be formed, is formed on the surface of a core wiringsubstrate, and thereafter, conductors, which comprise the interlayershorting parts, are formed inside the through holes in the insulatinglayer, a wiring layer is formed on the surface of the insulating layer,and the process is repeated a prescribed number of times to obtain thedesired multilayer wiring board.

Known methods of forming the insulating layer with through holes on thesurface of a core wiring substrate in the above-described processinclude the method of coating a liquid radiation-curing resin materialon the surface of the core wiring substrate and thereafter performing anexposure treatment and a development treatment on the coated film toform an insulating layer with through holes corresponding to the desiredshorting parts (via holes), and the method of coating a liquidthermosetting resin material or setting a sheet-like thermosetting resinmaterial on the surface of the core substrate, performing heat treatmentto form the insulating layer, and then illuminating laser light on theinsulating layer to form through holes corresponding to the desiredinterlayer shorting parts.

Further known methods of forming conductors inside the through holes ofan insulating layer include the method of forming metal thin films bydeposition of metal on the inner surfaces of the through holes of theinsulating layer by electroless deposition and then performingelectroplating, using the metal thin films as electrodes, to depositmetal and thereby form conductors comprised of metal layers of therequired thickness, the method of depositing metal on the inner surfacesof the through holes of the insulating layer by electroless depositionto form conductors comprised of metal layers of the required thickness,the method of filling the interiors of the through holes of theinsulating layer with an abovementioned conductive paste, for example,by screen printing or other printing method and then curing theconductive paste to form conductors, with which conductive powder isdispersed within a thermosetting resin, and the like.

However, with the above-described plating methods, since the rate atwhich a plated film grows from the metal ions is slow, a considerableamount of time is required to form a metal layer of the requiredthickness in cases where a rather thick conductive film (for example,with a film thickness of 10 μm or more), a conductive layer that fillsthe abovementioned through hole, via hole, an abovementioned interlayershorting part, or the like is to be formed. A high productivitytherefore cannot be achieved. Especially with the above-describedbuild-up method, since the interlayer shorting parts, which pass throughan insulating layer in its thickness direction, must be formed each timethe insulating layer is formed, the slowness of the rate of depositionof metal by plating has a large influence on the productivity.

Also, with methods of forming a conductive layer by coating, printingand the like using a conductive paste or ultrafine metal particledispersive solution, it is difficult to perform precise control of thethickness of the conductive layer that is obtained, the formationposition of the conductive layer and the like. In particular, since aconductive paste that is comprised of resin and conductive powder isrelatively high in viscosity (for example, approximately 100 Pa·s at 25°C.) in general, it is difficult to form conductive layers that are highin the precision of formation position, shape and the like. Also in thecase where the diameter of the through holes of the insulating layer issmall (for example, less than 100 μm in diameter), the interiors of thethrough holes cannot be filled readily with a conductive paste of suchhigh viscosity, and thus a multilayer wiring board of high connectionreliability cannot be obtained.

Also, with the method described in Japanese Unexamined PatentPublication No. Hei-9-134891, though the viscosity of the ultrafinemetal particle dispersive solution can be made low, since the dispersiondoes not contain a resin component, the conductive layer becomes crackedin cases where a thick conductive layer is to be formed. This methodalso has a problem in that the adhesion of the conductive layer to thesubstrate is low.

A purpose of the present invention is to provide an aqueous dispersionforming conductive layer, with which a conductive layer of highprecision can be formed efficiently by the electrodeposition method, aconductive layer formed from the aqueous dispersion, and an electronicpart and a circuit board having the conductive layer.

Another object of the present invention is to provide a highly efficientand highly precise circuit board manufacturing method that includes aprocess of forming a conductive layer using the abovementioned aqueousdispersion forming conductive layer as the electrodeposition solution.

Yet another object of the present invention is to provide a multilayerwiring board, which is high in productivity and connection reliability,and a manufacturing method thereof.

DISCLOSURE OF THE INVENTION

According to the invention, the above objects are achieved by theprovision of an aqueous dispersion forming conductive layer, aconductive layer, an electronic part, a circuit board and amanufacturing method thereof, and a multilayer wiring board and amanufacturing method thereof of the following arrangements.

[1]. An aqueous dispersion forming conductive layer characterized inthat conductive microparticles, with a number-average particle diameterof 1 μm or less, and organic particles, which are comprised of at leastone of either a polymerizable compound or a polymer, are dispersed in anaqueous medium and in enabling the formation of a conductive layer byelectrodeposition.

[2]. An aqueous dispersion forming conductive layer as set forth in [1]above, wherein the volume ratio of the abovementioned conductivemicroparticles to the abovementioned organic particles is 99:1 to 40:60.

[3]. An aqueous dispersion forming conductive layer as set forth in [1]or [2] above, which is prepared by mixing a conductive microparticledispersive solution, in which the abovementioned conductivemicroparticles are dispersed in an organic solvent, and an organicparticle dispersive solution, in which the abovementioned organicparticles are dispersed in an aqueous medium.

[4]. An conductive layer characterized in being formed byelectrodeposition using a aqueous dispersion forming conductive layer asset forth in any one of [1] to [3] above and in that the volumeresistivity is 10⁻⁴ Ω·cm or less.

[5]. An electronic part characterized in being equipped in a conductivelayer formed by electrodeposition using an aqueous dispersion formingconductive layer as set forth in any one of [1] to [3] above.

[6]. A circuit board characterized in having an insulating layer and aconductive layer, which is formed by an electrodeposition method usingan aqueous dispersion forming conductive layer as set forth in any oneof [1] to [3] above as an electrodeposition solution and includesconducting through parts that pass through the abovementioned insulatinglayer.

[7]. A circuit board manufacturing method characterized in using anaqueous dispersion forming conductive layer as set forth in any one of[1] to [3] above and being comprised of;

(a) a process of forming through holes in an insulating layer,

(b) a process of setting a conductive foil on a part of one surface ofthe abovementioned insulating layer that includes the openings at oneend of the abovementioned through holes, and

(c) a process of forming conducting through parts inside theabovementioned through holes by an electrodeposition method using theabovementioned aqueous dispersion forming conductive layer as theelectrodeposition solution and using the abovementioned conductive foilas one of the electrodes.

[8]. A circuit board manufacturing method characterized in using anaqueous dispersion forming conductive layer as set forth in any one of[1] to [3] above and being comprised of;

(a) a process of forming an insulating layer on a core wiring substrateon which a conducting pattern has been formed,

(b) a process of patterning the abovementioned insulating layer andforming an insulating layer pattern in through holes that expose a partof the abovementioned conducting pattern,

(c) a process of forming an electroless plated layer at parts includingthe interiors of the abovementioned through holes by electrolessdeposition using the abovementioned insulating layer pattern as a maskmaterial, and

(d) a process of forming a conductive layer, which includes conductingthrough parts at interiors of the abovementioned through holes, byelectrodeposition using the abovementioned aqueous dispersion formingconductive layer as an electrodeposition solution and using theabovementioned conducting pattern and the abovementioned electrolessplated layer as one of electrodes.

[9]. A circuit board manufacturing method characterized in that aplurality of circuit boards, obtained by a method set forth in [7] or[8] above, are laminated.

[10]. A multilayer wiring board characterized in having a core wiringsubstrate, which is arranged by forming substrate wiring layers that aremutually connected electrically on both surfaces of an insulatingsubstrate, an insulating layer, which is laminated onto at least onesurface of the core wiring substrate, a wiring layer, which is formed onthe abovementioned insulating layer, and interlayer shorting parts,which extend through the abovementioned insulating layer in thethickness direction and electrically connect the abovementioned wiringlayer to the abovementioned substrate wiring layer,

the abovementioned multilayer wiring board being characterized in thateach of the abovementioned interlayer shorting parts is comprised of aconductor, in which conductive microparticles are contained inside apolymer substance, and in that the abovementioned conductor is formed byelectrodeposition in an electrodeposition solution, in which conductivemicroparticles and organic particles, comprised of at least one ofeither a polymerizable compound or a polymer, are dispersed in anaqueous medium.

[11]. A multilayer wiring board as set forth in [10] above, wherein theabovementioned core wiring substrate has substrate shorting parts, whichelectrically connect the abovementioned substrate wiring layers, formedon both sides of the abovementioned insulating substrate, to each otherand extend through the abovementioned insulating substrate in thethickness direction,

each of the abovementioned substrate shorting parts is comprised of aconductor, in which conductive microparticles are contained inside apolymer substance, and the abovementioned conductor is formed byelectrodeposition in an electrodeposition solution, in which conductivemicroparticles and organic particles, comprised of at least one ofeither a polymerizable compound or a polymer, are dispersed in anaqueous medium.

[12]. A multilayer wiring board as set forth in [10] or [11] above,wherein the proportion as volume percentage of the abovementionedconductive microparticles in the abovementioned conductors that comprisethe abovementioned interlayer shorting parts and/or substrate shortingparts is 40 to 99%.

[13]. A method of manufacturing a multilayer wiring board as set forthin any of [10] to [12] above, characterized in being comprised of;

a process of preparing a core wiring substrate member, which iscomprised of an insulating substrate, a substrate wiring layer, formedon one surface of the abovementioned insulating substrate, and a metallayer, formed on the other surface of the abovementioned insulatingsubstrate and electrically connected to the abovementioned substratewiring layer,

a process of forming an insulating layer, having through holes formed incorrespondence to interlayer shorting parts to be formed on thesubstrate wiring layer, on one surface of the abovementioned core wiringsubstrate member, and

a process of forming conductors that comprise the abovementionedinterlayer shorting parts inside the abovementioned through holes of theabovementioned insulating layer by electrodeposition using anelectrodeposition solution, in which conductive microparticles andorganic particles comprised of at least one of either a polymerizablecompound or a polymer, are dispersed in an aqueous medium, with theabovementioned substrate wiring layer of the core wire substrate memberon which the abovementioned insulating layer was formed, as a depositionelectrode.

[14]. A multilayer wiring board manufacturing method as set forth in[13] above, wherein a substrate forming material, having an insulatingsubstrate and a metal layer, formed on at least one surface of theabovementioned insulating substrate, is prepared, through holes, whichpass through the abovementioned insulating substrate of theabovementioned substrate forming material in the thickness directionthereof, are formed, and

after performing electrodeposition, using the abovementioned metal layerof the abovementioned substrate forming material as the depositionelectrode, in an electrodeposition solution, in which conductivemicroparticles and organic particles comprised of at least one of eithera polymerizable compound or a polymer, are dispersed in an aqueousmedium, to form conductors that comprise substrate shorting parts insidethe abovementioned through holes of the abovementioned insulatingsubstrate, a substrate wiring part is formed on one surface of theabovementioned insulating substrate to form the abovementioned corewiring substrate member.

[15]. A multilayer wiring board manufacturing method as set forth in[13] or [14] above, wherein the volume ratio of the abovementionedconductive microparticles to the abovementioned organic particles is99:1 to 40:60.

The invention shall now be described in further detail.

(a)Conductive Microparticles

Though the material that comprises the conductive microparticles used inthe invention is not restricted in particular as long as it exhibitsconductivity, a material that is not oxidized readily is preferable inthat stable conductivity can be provided over a long term. Specificexamples of such a material includes a metal selected from among gold,silver, copper, aluminum, zinc, nickel, palladium, platinum, cobalt,rhodium, iridium, iron, ruthenium, osmium, chromium, tungsten, tantalum,titanium, bismuth, lead, boron, silicon, tin, barium and alloys of thesemetals and the like. Two or more types of conductive materials made ofdiffering materials ray also be used in combination. The conductivemicroparticles are preferably comprised of a material with a volumeresistivity of 10⁻⁵ Ω·cm or less and are more preferably comprised of amaterial with a volume resistivity of 7×10⁻⁶ Q·cm or less.

In the invention of the first to ninth claims, the number-averageparticle diameter of the abovementioned conductive microparticles mustbe 1 μm or less and is preferably 0.5 μm or less and more preferably 0.3μm or less. When the number-average particle diameter exceeds 1 μm, theparticles tend to settle readily in the aqueous dispersion formingconductive layer of the invention and the storage stability of theaqueous dispersion will be inadequate. Though the lower limit of thenumber-average particle diameter is not restricted in particular, it isnormally 0.02 μm or more. The conductive microparticles of the tenth tofifteenth claim of the invention also preferably have a number-averageparticle diameter in the range given above. In the specification,“particle diameter” shall refer to the primary particle diameter.

Metal microparticles, produced by the gas phase vaporization method,electrolysis method, reduction method and the like, are favorably usedas the conductive microparticles due to the ease of production.

The conductive particles having a spherical shape, angular shape,scale-like shape, spike-like shape and the like may be used as theconductive particles of the invention. Among these, the conductiveparticles of angular shape or scale-like shape are especially preferablein that the inter-particle contact area will be high.

(b)Organic Particles

(b-i) Composition of Organic Particles

The organic particles in the invention are comprised of “at least one ofeither a polymerizable compound or a polymer.” Here, a “polymerizablecompound” refers to a compound having a polymerizable group and refersinclusively to precursor polymers prior to complete curing,polymerizable oligomers, monomers or the like. On the other hand,“polymer” refers to a compound for which the polymerization reaction hasbeen practically completed. The polymer may also be one that can becrosslinked after electrodeposition by means of heat, moisture and thelike.

The abovementioned organic particles preferably have an electricalcharge on the surface in order to enable electrodeposition. The surfacecharge may be anionic or cationic. In the case where the material of theconductive microparticles is copper, the surface charge of the organicparticles is preferably cationic since the preservation stability of theaqueous dispersion that contains these particles will then be better.

The abovementioned organic particles are preferably comprised of atleast one type of substance or two or more types of substances selectedfrom among acrylic-based resins, epoxy-based resins, polyester-basedresins, and polyimide-based resins. The organic particles may containother components in addition to these resins. These resins may also bechemically bonded to each other or to other components.

In the invention, in the case where the resin component is to bedecomposed and eliminated by heating or the like afterelectrodeposition, the use of organic particles having an acrylic-basedresin as the principal component is especially preferable. On the otherhand, if the elimination by decomposition is not to be performed, theuse of the organic particles having polyimide-based resin as theprincipal component is especially preferable since a conductive layerthat is excellent in mechanical characteristics, chemicalcharacteristics, and electrical characteristics can then be formedreadily. Here, “polyimide-based resin” refers inclusively to polyimideresins, precursor polymers that can be cured by heating afterelectrodeposition (for example, polyamic acid and the like), copolymerresins of a monomer used in forming a polyimide resin and anothermonomer and precursor polymers of such copolymer resins, reactionproducts of a polyimide resin or a precursor polymer of a polyimideresin and another compound, monomers and oligomers used in formingpolyimide-based resins or the like. The same applies to the other resinsas well.

(b-2) Aqueous Emulsion of Organic Particles

An aqueous dispersion of the invention is normally prepared using anaqueous emulsion in which the above-described organic particles aredispersed in an “aqueous medium.”

In the following, the methods of producing an aqueous emulsion oforganic particles mainly comprised of acrylic-based resin (referred tohereinafter as “acrylic-based resin emulsion”), an aqueous emulsion oforganic particles mainly comprised of epoxy-based resin (referred tohereinafter as “epoxy-based resin emulsion”), an aqueous emulsion oforganic particles mainly comprised of polyester-based resin (referred tohereinafter as “polyester-based resin emulsion”), and an aqueousemulsion of organic particles mainly comprised of polyimide-based resin(referred to hereinafter as “polyimide-based resin emulsion”) shall bedescribed.

(i)Method of Producing an Acrylic-based Resin Emulsion

The method of producing an acrylic-based resin emulsion is notrestricted in particular, and such an emulsion can for example beproduced by the ordinary emulsion polymerization method, by the methodof adding a reaction solution, with which polymerization has beencarried out in alcohol or other organic solution, to water whilestirring to disperse the resin and the like. As the monomer, one or twoor more types of monomers selected from among generally used acrylicand/or methacrylic monomers may be used. In order to enableelectrodeposition of the organic particles that are obtained, a monomerhaving a cationic group or anionic group is usually copolymerized. Thecopolymerization ratio is preferably set to 5 to 80% by weight (or morepreferably 10 to 50% by weight) of the total amount of monomers used.

(ii)Method of Producing an Epoxy-based Resin Emulsion

The method of producing an epoxy-based resin emulsion is not restrictedin particular and priorly known methods, for example, the methodsdisclosed in Japanese Unexamined Patent Publication No. Hei-9-235495,ibid. No. Hei-9-208865 may be used.

(iii)Method of Producing a Polyester-based Resin Emulsion

The method of producing a polyester-based resin emulsion is notrestricted in particular and priorly known methods, for example, themethods disclosed in Japanese Unexamined Patent Publication No.Sho-57-10663, ibid. No. Sho-57-70153, ibid. No. Sho-58-174421, may beused.

(iv)Method of Producing a Polyimide-based Resin Emulsion

The method of producing a polyimide-based resin emulsion is notrestricted in particular and the following two types of emulsions andmethods may be given as examples of polyimide-based resin emulsions andproduction methods thereof that can be used favorably in the invention.

(1)A polyimide-based resin emulsion comprised of composite particles of(A) a polyimide that is soluble in an organic solvent and (B) ahydrophilic polymer. The type of polyimide-based resin emulsion can beproduced favorably for example by the method described in JapaneseUnexamined Patent Publication No. Hei-11-49951.

(2)A polyimide-based resin emulsion comprised of composite particles of(C) a polyamic acid and (D) a hydrophobic compound. The type ofpolyimide-based resin emulsion can be produced favorably for example bythe method described in Japanese Unexamined Patent Publication No.Hei-11-60947.

These polyimide-based emulsions are excellent in preservation stabilityas aqueous dispersions and favorable in that by electrodeposition of theparticles in the emulsion, an electrodeposited film can be formed withwhich the inherent heat resistance, electrical insulation, chemicalresistance or the like of polyimide are maintained.

Methods of producing a polyimide-based resin emulsion used in (1) aboveshall now be described in more detail.

The method of synthesizing the “(A) polyimide that is soluble in anorganic solvent” is not restricted in particular, and the polyimide maybe synthesized for example by mixing and condensation polymerizing atetracarboxylic dianhydride with a diamine compound to obtain a polyamicacid and then subjecting the polyamic acid to a dehydration ring-closingreaction by thermal imidization or chemical imidization. A polyimidewith a block structure may also be synthesized by performingcondensation polymerization of a tetracarboxylic dianhydride with adiamine compound in multiple stages.

The polyimide soluble in organic solvent preferably has one or morereactive groups (a), for example, the carboxyl group, amino group,hydroxyl group, sulfonic group, amide group, epoxy group, isocyanategroup and the like. Examples of methods of synthesizing a polyimide witha reactive group (a) include the method of using a compound having thereactive group (a) as the carboxylic dianhydride, diamine compound,carboxylic monoanhydride, monoamine compound, or other reaction rawmaterial used in the synthesis of polyamic acid and keeping the reactivegroup (a) after the dehydration ring-closing reaction.

The “(B) hydrophilic polymer” is comprised of a hydrophilic polymerhaving one or more types of hydrophilic groups, such as the amino group,carboxyl group, hydroxyl group, sulfonic group, amide group or the like,and having a solubility in water at 20° C. of normally 0.01 g/100 g ormore and preferably 0.05 g/100 g or more. In addition to theabovementioned hydrophilic group, the hydrophilic polymer preferably hasone or more reactive groups (b) that can react with the reactive group(a) in the above-described component (A). Examples of such a reactivegroup (b) include the epoxy group, isocyanate group, carboxyl group, aswell as the same groups given above as hydrophilic groups. Such ahydrophilic polymer can be obtained by homopolymerization orcopolymerization of a monovinyl monomer or monovinyl monomers with thehydrophilic group and/or reactive group (b) or by copolymerizing such amonovinyl monomer with another type of monomer.

The (A) polyimide that is soluble in an organic solvent and the (B)hydrophilic polymer are selected so that the resulting combination willbe one with which the reactive group (a) and the reactive group (b) inthe hydrophilic polymer will exhibit an appropriate reactivity, and thepolylmide and the hydrophilic polymer are mixed in solution form in anorganic solvent for example and heated as necessary to cause the twocomponents to react. The reaction solution is then mixed with an aqueousmedium, and depending on the case, at least part of the organic solventis removed to obtain a polyimide-based resin emulsion comprised ofcomposite particles with which the polyimide and the hydrophilic polymerare contained in the same particle in a mutually bonded condition.

Methods of producing a polyimide-based resin emulsion used in (2) aboveshall now be described in more detail.

The method of synthesizing the “(C) polyamic acid,” which is theprecursor of polyimide, is not restricted in particular, and thepolyamic acid may be obtained by subjecting a tetracarboxylicdianhydride and a diamine compound to condensation polymerization in apolar organic solvent. A polyamic acid with a block structure may alsobe synthesized by performing condensation polymerization of atetracarboxylic dianhydride with a diamine compound in multiple stages.A polyamic acid, which has been partially imidized by dehydrationring-closing of a polyamic acid, may also be used.

Meanwhile, the “(D) hydrophobic compound” is a compound having a group(referred to hereinafter as the “reactive group”) that can react with atleast the amic acid group in the above-described polyamic acid. Examplesof the reactive group include the epoxy group, isocyanate group,carbodiimide group, hydroxyl group, mercapto group, halogen group, alkylsulf onyl group, aryl sulfonyl group, diazo group, carbonyl group andthe like. One or more such reaction groups may exist in the hydrophobiccompound. “Hydrophobic” normally signifies that the solubility in waterat 20° C. is less than 0.05 g/100 g, and the solubility is preferablyless than 0.01 g/100 g and more preferably less than 0.005 g/100 g.

One or two or more types of compounds selected for example from amongepoxidized polybutadienes, bisphenol A type epoxy resins,naphthalene-based epoxy resins, fluorene-based epoxy resins, biphenyltype epoxy resins, glycidyl ester type epoxy resins, aryl glycidylethers, glycidyl (meth)acrylate, 1,3,5,6-tetraglycidyl-2,4-hexanediol,N,N,N′,N′-tetraglycidyl-m-xylenediamine, tolylene diisocyanate,dicyclohexylcarbodiimide, polycarbodiimide, cholesterol, benzyl alcoholp-toluenesulfonic acid ester, ethyl chloroacetate, triazine trithiol,diazomethane, diacetone (meth)acrylamide and the like may be used.

This (C) polyamic acid and (D) hydrophobic compound are reacted, forexample, upon mixing in a solution condition in an organic solvent. Thereaction solution is then mixed with an aqueous medium, and, dependingon the case, at least part of the organic solvent is removed to obtain apolyimide-based resin emulsion comprised of composite particles withwhich the polyamic acid and the hydrophobic compound are contained inthe same particle.

The tetracarboxylic dianhydride used in the above-described methods of(1) and (2) is not restricted in particular, and examples includealiphatic tetracarboxylic dianhydrides and alicyclic tetracarboxylicdianhydrides, such as butanetetracarboxylic dianhydride,1,2,3,4-cyclobutanetetracarboxylic dianhydride,3,3′,4,4′-dicyclohexyltetracarboxylic dianhydride,2,3,5-tricarboxycyclopentylacetic dianhydride,1,3,3a,4,5,9b-hexahydro-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-c]-furan-1,3-dioneor the like; and

aromatic tetracarboxylic dianhydrides, such as pyromellitic dianhydride,3,3′, 4,4′-benzophenonetetracarboxylic dianhydride, 3,3′,4,4′-biphenylsulfonetetracarboxylic dianhydride or the like. Thesetetracarboxylic dianhydrides may be used solitarily or two or more ofthese tetracarboxylic dianhydrides may be used in mixed form.

The diamine compound used in the above-described methods of (1) and (2)is not restricted in particular, and examples include aromatic diamines,such as p-phenylenediamine, 4,4′-diaminodiphenylmethane,2,2-bis[4-(4-aminophenoxy)phenyl]propane or the like;

alicyclic diamines, such as 1,1-metaxylilenediamine, 1,3-propanediamine,tetramethylenediamine, 4,4′-methylene-(bis(cyclohexylamine) or the like;

diamines having two primary amino groups and nitrogen atoms besidesthose of the primary amino groups in the molecule, such as2,3-diaminopyridine, 2,4-diamino-6-dimethylamino-1,3,5-triazine,2,4-diamino-5-phenylthiazole, bis(4-aminophenyl)phenylamine or the like;

monosubstituted phenylenediamines; and

diamino organosiloxanes.

These diamine compounds may be used solitarily or two or more suchcompounds may-be used in mixed form.

(c)Aqueous Dispersion

An aqueous dispersion of the invention has the above-describedconductive microparticles and the above-described organic particlesdispersed in an aqueous medium. In the specification, “aqueous medium”refers to a medium containing water, and the water content of theaqueous medium is normally 0.5% by weight or more and preferably 10% byweight or more. A water content of less than 0.5% by weight or more isunfavorable as it will be difficult to use such an aqueous dispersiondirectly as an electrodeposition solution. On the other hand, since thedispersion stability of the conductive microparticles and the like willbe lowered when the water content is too high, the water content ispreferably 50% by weight or less, more preferably 40% by weight or less,and even more preferably 20% by weight or less.

Examples of other media used as necessary along with water include thenonprotonic polar solvents used in the above-described production ofpolyamic acid or polyimide, esters, ketones, phenols, alcohols, aminesor the like. Among these, an alcohol comprised of one or two or moretypes of alcohols with 1 to 10 carbon atoms is preferably contained atan amount of 10 to 90% by weight (more preferably 20 to 70% by weight)from the point of dispersion stability of the metal microparticles toserve as conductive microparticles. Also, the aqueous medium preferablycontains an amine, such as monoethanolamine, diethanolamine and thelike, at an amount of 0.01 to 5% by weight (more preferably 0.1 to 1% byweight), and the dispersion stability is thereby improved.

The volume ratio of conductive microparticles to organic particlescontained in the aqueous dispersion is preferably in the range of 99:1to 40:60, more preferably in the range of 95:5 to 40:60, and even morepreferably in the range of 85:15 to 60:40. When the proportion of thetotal amount of conductive microparticles and organic particles that iscomprised by the conductive microparticles is less than 40% by volume,the volume resistivity will be too great and the conductive layer willnot be fit for practical use. Meanwhile, if the proportion of theconductive microparticles exceeds 80% by volume, the film formingproperty, shape maintaining property, adhesion to the substrate or thelike will tend to be inadequate and cracks may form in the conductivelayer.

The pH of the aqueous dispersion is preferably 3 to 12 (more preferably4 to 10), the solids concentration is preferably 1 to 50% by weight(more preferably 5 to 30% by weight), and the viscosity at 20° C. ispreferably 1 to 100 mPa·s. When the pH, solids concentration, orviscosity fall outside these ranges, the storage stability may becomepoor due to poor dispersion of the particles, the productivity may belowered due to an inadequate rate of electrodeposition, workability inhandling and use may be lowered, and electrodeposition onto parts offine shape, such as the interiors of the through holes, may becomedifficult.

The aqueous dispersion is favorably prepared by mixing a conductivemicroparticle dispersive solution, with which the above-describedconductive microparticles are dispersed in an organic solvent, and anorganic particle dispersive solution (preferably an above-describedaqueous emulsion), with which the above-described organic particles aredispersed in an aqueous medium.

As the organic solvent to be used in the abovementioned “conductivemicroparticle dispersive solution,” an alcohol-based solvent, comprisedof one or two or more types of alcohols with 1 to 10 carbon atoms, ispreferable in terms of dispersion stability, solubility in the medium ofthe aqueous dispersion or the like, and ethyl alcohol, isopropylalcohol, or a mixed solvent of these is used especially preferably.Methods of dispersing the conductive microparticles in the organicsolvent include methods of using a homomixer, high-pressure homogenizer,ultrasonic mixer or the like and methods in which these are combined.The conductive microparticle dispersive solution contains the conductivemicroparticles at an amount of preferably 3 to 40% by weight and morepreferably 5 to 30% by weight.

In addition to the above-described conductive microparticles andabove-described organic particles, an aqueous dispersion of theinvention may contain at least one type of compound (referred tohereinafter as “organosilane condensate, etc.”) selected from amongorganosilanes expressed by the formula (1) given below, hydrolyzates,with which all or part of the hydrolyzable groups of such anorganosilane have been hydrolyzed, and partial condensates, resultingfrom the partial dehydration condensation of such hydrolyzates.Especially in the case where curing by heat is performed afterelectrodepOSition, the conductive layer that is formed from such anaqueous dispersion is made excellent in mechanical characteristics andchemical characteristics by the crosslinking of the organosilanecondensate, etc. in the conductive layer.

(R¹)_(n)Si(OR²)_(4−n)  (1)

(In the above formula, R¹ indicates the hydrogen group or a monovalentorganic group with 1 to 8 carbons, R² indicates an alkyl group with 1 to5 carbon atoms, an acyl group with 1 to 6 carbons, or the phenyl group,and n is an integer of value 1 or 2. R¹ and R² may be the same or maydiffer from each other.)

Examples of the organic group with 1 to 8 carbons of R¹ in the aboveformula (1) include straight-chain and branched alkyl groups,halogenated alkyl groups, vinyl groups, phenyl group,3,4-epoxycyclohexylethyl group and the like. R¹ may contain a carbonylgroup. R¹ is preferably an alkyl group with 1 to 4 carbons or the phenylgroup.

Examples of the alkyl group with 1 to 5 carbons or acyl group with 1 to6 carbons of R² include the methyl group, ethyl group, n-propyl group,isopropyl group, n-butyl group, isobutyl group, sec-butyl group,tert-butyl group, n-pentyl group, acetyl group, propionyl group, butyrylgroup and the like. R² is preferably an alkyl group with 1 to 4 carbons.

Examples of preferably used organosilanes includedimethyldimethoxysilane, dimethyldiethoxysilane,isobutyltrimethoxysilane, and phenyltriethoxysilane. Just one suchorganosilane may be used or two or more such organosilanes may be usedin combination.

The above-described “organosilane condensate, etc.” preferably forms acomposite particle with the above-described organic particle in anaqueous dispersion of the invention. Here, “composite particle” refersto a particle in which the compound that comprises the above-describedorganic particle is chemically bonded to the organosilane condensate,etc., a particle with which the organosilane condensate, etc. isadsorbed on the surface or interior of the above-described organicparticle and the like.

The usage amount of the organosilane condensate is preferably 0.1 to 500weight parts and more preferably 0.5 to 250 weight parts to 100 weightparts of the above-described organic particles. When the usage amount ofthe organosilane condensate, etc. is less than 0.1 weight parts, thedesired effects may not be obtained, and when the usage amount of theorganosilane condensate, etc. is greater than 500 weight parts, theadhesive property of the conductive layer and the like tends to belowered.

Such composite particles may be produced by the following method (1) or(2) or the like. These methods may also be combined.

[1]An abovementioned organosilane is added to an emulsion of theabove-described organic particles, and after making at least part of theorganosilane be absorbed by the above-described organic particles,hydrolysis and condensation of the organosilane are made to proceed.

[2]A reaction that generates the above-described organic particles iscarried out under the presence of an abovementioned organosilanecondensate, etc., which has been dispersed in an aqueous medium.

In order to make an organosilane be absorbed by the organic particles inthe above-described method [1], the organosilane may be added to anemulsion and stirred adequately. In this case, preferably 10% by weightor more (more preferably 30% by weight or more) of the addedorganosilane is made to be absorbed by the particles. In order toprevent progress of the hydrolysis and condensation of the organosilaneat a stage at which absorption is inadequate, the pH of the reactionsystem may be adjusted to normally 4 to 10, preferably 5 to 10, and morepreferably 6 to 8. The treatment temperature for making the organosilanebe absorbed by the organic particles is set preferably to 70° C. orless, more preferably to 50° C. or less, and even more preferably to 0to 30° C. The duration of treatment is normally set to 5 to 180 minutesand preferably set to approximately 20 to 60 minutes.

The temperature at which the absorbed organosilane is hydrolyzed andcondensed is normally 30° C. or more, preferably 50 to 100° C., and morepreferably 70 to 90° C. The duration of polymerization is preferably 0.3to 15 hours and more apreferably 1 to 8 hours.

In the above-described method [2], the abovementioned organosilane ismixed in an aqueous solution of a strongly acidic emulsifier, such as analkylbenzenesulfone, using a homomixer or an ultrasonic mixer or thelike and thereby hydrolyzed and condensed to obtain an organosilanecondensate or the like that is dispersed in an aqueous medium. Under thepresence of the organosilane condensate, etc., the above-describedorganic particles are formed, preferably by emulsion polymerization.

(d)Conductive Layer

Though an aqueous dispersion of the invention is normally used in itsoriginal concentration as the electrodeposition solution for forming theconductive layer, it may also be diluted or concentrated. Apriorly-known additive may also be blended suitably as necessary. By anormal electrodeposition method using the electrodeposition solution,the conductive microparticles and the organic particles in the aqueousdispersion can be electrodeposited onto an electrode surface and thelike to produce a conductive layer.

After the electrodeposition process, the electrical resistance of theconductive microparticle interface is lowered by the following methods.

{circumflex over (1)} In order to eliminate metal oxides and othernon-conductive substances that exist on the surface of the conductivemicroparticles, the layer formed by electrodeposition is baked under areducing atmosphere. For example, metal oxides can be reduced by bakingat a temperature of 200 to 500° C. for 30 to 180 minutes under an inertgas atmosphere having 0.1 to 5% by volume of hydrogen mixed in. Thesurface of this layer may also be washed by a weakly acidic, 50 to 100%aqueous solution of acetic acid, formic acid, propionic acid or the liketo eliminate the metal oxides and other non-conductive substances bydissolution.

{circumflex over (2)} A metal is deposited onto the surface of theconductive microparticles. A metal can be deposited efficiently onto themicroparticle interface by immersion in an electroplating solution andapplication of a current in the form of pulses. The proportion of theconduction time with respect to a single pulse cycle is set preferablyto 0.6 or less and more preferably to 0.3 or less. Known metals, such ascopper, nickel, gold, platinum, silver, tin, solder alloy and the likemay be used as the metal to be electroplated.

The resin component of the electrodeposited particles may also beeliminated by decomposition to lower the volume resistivity of theconductive layer. In this case, an acrylic-based resin, which can beeliminated by decomposition at a relatively low temperature, ispreferably used as the resin component, and the resin component can beeliminated substantially by heating at 200 to 800° C. for 30 to 180minutes. In the case where the layer is baked under a reducingatmosphere as has been described above, the resin component can beeliminated by decomposition at the same time as this baking.

Also, a thermosetting resin may be used as the resin component and theresin component may be cured by heating further after electrodeposition.In this case, an aqueous dispersion containing the abovementionedorganosilane condensate, etc. is preferably used. An epoxy-based resinor a polyimide-based resin is preferably used as the thermosettingresin, and the use of a polyimide-based resin is most preferable. Thoughthe thermosetting conditions are not restricted in particular as long asthe temperature is not one at which the resin component will beeliminated by decomposition, the heating temperature is preferably 100to 400° C. and more preferably 150 to 300° C. The heating duration ispreferably 5 minutes or more and more preferably 10 minutes or more. Bythermosetting the resin component, the mechanical characteristics of theconductive layer is improved, and by the quenching, the conductive layeris made dense, thereby improvingtheelectricalcharacteristics.Furthermore, since the resin component that remains in the conductivelayer functions as a binder, a conductive layer that is excellent inadhesive property, impact resistance and the like can be formed. In thecase where the film is to be baked under a reducing atmosphere as hasbeen described above, the resin component may be thermoset using theheat of baking.

According to the aqueous dispersion of the invention, a conductive layerwith a volume resistivity of 10⁻⁴ Ω·cm or less (or more preferably0.5×10⁻⁴ Ω·cm or less) can be obtained. In the case where the conductivelayer is to be formed as a film, the thickness thereof is preferably 1to 80 μm (more preferably 3 to 50 μm and even more preferably 5 to 20μm). This is because the advantages of production by electrodepositionusing an aqueous dispersion of the invention are exhibited effectivelyin the forming of a conductive layer with a thickness within this range.

(e)Electronic Part

According to the aqueous dispersion of the invention, a conductive layerof high precision of film thickness and the like can be producedefficiently. A conductive layer can also be formed efficiently at highprecision at parts of fine shapes, such as the through holes, via holesand the like that are made through the insulating layer. The conductivelayer is favorably applied to electronic parts such as conductivecircuits, bumps, and wiring substrates made by combining such components(for example, multilayer circuit boards).

(f)Circuit Board

(f-1) Arrangement

A circuit board of the invention is equipped with an insulating layerand a conductive layer, which is formed using the above-describedaqueous dispersion forming conductive layer. A part of the conductivelayer comprises the conducting through parts that pass through theabovementioned insulating layer.

The material that comprises the insulating layer is not restricted inparticular, and polyimide resin, epoxy-based resin, bismaleimide-basedresin, phenol-based resin and the like may be used in accordance to theapplication of the circuit board that is obtained. For example, a glassepoxy substrate, BT resin substrate or the like, which is generally usedas a core substrate in a build-up wiring board, or an epoxy-based resinlayer, polyimide-based resin layer or the like, which is used as aninsulating layer in a build-up wiring board, may be used favorably.Though the thickness of insulating layer is also not restricted inparticular, it is normally 20 to 150 μm (preferably 50 to 100 μm) in thecase of a core substrate and normally 5 to 100 μm (preferably 10 to 50μm) in the case of a build-up insulating layer.

A polyimide-based resin layer comprised of a polyimide-based compositewith an elastic modulus of less than 10GPa is especially favorably usedas the polyimide-based resin layer to be employed as the insulatinglayer. As such a polyimide-based composite, a composite, comprised of a(A) polyimide component and (B) another polymer component as disclosedin laid-open Japanese patent publication No. 2000-44800, may be used.The (A) polyimide component is preferably soluble in an organic solvent,and a polyimide with a block structure, a terminal-modified polyimide, apolyimide, polyamic acid or the like with a reactive group can be usedfavorably. The (B) other polymer component preferably has a reactivegroup that can react directly or indirectly via a crosslinking agentwith the (A) polyimide component. Specific examples of the (B) otherpolymer component include acryl polymers and other polymers of vinylmonomers, natural rubbers and epoxidized products thereof,polybutadienes and epoxidized products thereof, styrene-butadienerubbers, isoprene rubbers, urethane rubbers, acrylonitrile rubbers,ethylene-propylene rubbers, fluoropolymers, silicone polymers and thelike.

The abovementioned conducting through parts are normally formed so as tofill up the through holes that pass through the abovementionedinsulating layer or are formed as films that line the wall surfaces ofthe through holes. The diameter of a through hole is preferably 4 to 150μm (more preferably 6 to 100 μm and even more preferably 10 to 90 μm).This is because with a through hole with a diameter in this range, theadvantages of forming a conducting through part in the interior thereofby electrodeposition using an aqueous dispersion of the invention areexhibited effectively. In the case where the conducting through part isformed as a film that lines the wall surface of a through hole, the filmthickness thereof is preferably 1 to 50 μm (more preferably 2 to 301 μmand even more preferably 3 to 20 μm).

(f-2) Manufacturing Method

The above-described circuit board can be manufactured for example by themethod of the seventh claim (this method shall also be referred tohereinafter as “Method 1”). The manufacturing process of this methodshall now be described with reference to FIG. 1.

First, as shown in FIG. 1(a), through holes 411 are formed in aninsulating layer 41. Next, as shown in FIG. 1(b), a conductive foil 42is laminated onto one surface 41 a of insulating layer 41. Theconductive foil 42 may cover the entirety or just a part of surface 41 abut is provided at least at a part that includes the openings at one endof through holes 411. That is, parts of conductive foil 2 form thebottom surfaces 421 of through holes 411. Thereafter, the substrateshown in FIG. 1(b) is immersed in and made to contact anelectrodeposition solution, comprised of an aqueous dispersion as setforth in any of the first to third claims, so that the electrodepositionsolution fills the through holes 411, and electrodeposition is thenperformed using conductive foil 42 as one of the electrodes. Conductivemicroparticles and organic particles are thereby electrodeposited ontothe bottom surfaces 421 as shown in FIG. 1(c) and conducting throughparts 431 are formed inside through holes 411.

Thereafter, another conductive foil 42 is laminated onto the othersurface 41 b of insulating layer 41 for example as shown in FIG. 1(d)and conductive foils 42 are etched by a priorly-known method to form aconducting patterns 44. A circuit board, with which a conducting pattern44, formed on surface 41 a, and a conducting pattern 44, formed onsurface 41 b, are connected by conducting through parts 431 as shown inFIG. 1(e) is thereby obtained. By appropriately heating the board in asuitable process after electrodeposition, the resin that formsconducting through parts 431 may be thermoset, and in the case whereinsulating layer 41 is comprised of a semi-cured resin, this can bethermoset at the same time at the stage.

The circuit board of the invention may also be manufactured by themethod of the eighth claim (also referred to hereinafter as “Method 2”).The manufacturing process of this method shall now be described withreference to FIG. 2.

A conductive layer is formed on a core wiring substrate on whichconducting patterns have been formed in advance with Method 2. As thecore wiring substrate, a core wiring substrate 48, which as shown inFIG. 2(a) is equipped with an insulating layer (also referred to as“core insulating layer”) 41, conducting pattern 44, and conductingthrough parts 431 and was manufactured by the processes or the likeillustrated in FIGS. 1(a) to (e), may be used.

As shown in FIG. 2(b), insulating layers 45 are formed on both surfacesof core wiring substrate 48 by coating of a photosensitive insulatingresin. By patterning the layer with a known method, insulating layerpatterns 46, with through holes 451 that expose parts of conductingpatterns 44, are formed as shown in FIG. 2(c). Next as shown in FIG.2(d), insulating layer patterns 46 are used as mask materials in formingelectroless plated layers 47 by electroless deposition with a knownmethod. Though these electroless plated layers 47 may be formed on theentire surface or just part of the substrate shown in FIG. 2(c), theyare formed at parts that at least include the interiors of through holes451 so as to be electrically connected with the conducting patterns 44positioned at the bottoms of through holes 451.

Thereafter, the substrate shown in FIG. 2(d) is immersed in and made tocontact an electrodeposition solution, comprised of an aqueousdispersion as set forth in any of the first to third claims, so that theelectrodeposition solution fills the through holes 451 andelectrodeposition is then performed using electroless plated layers 47as one of the electrodes. Conductive microparticles and organicparticles are thereby electrodeposited onto the electroless platedlayers 47 as shown in FIG. 2(e), thereby forming conducting layers 43that include the conducting through parts 432 formed inside throughholes 451.

For the substrate shown in FIG. 2(e), a circuit board obtained by themethod of the eighth claim is laminated on each of the surfaces of acircuit board obtained by the method of the seventh claim. By performingthe patterning of conductive layers 43 from the condition and thereafterrepeating the processes of FIGS. 2(b) to (e), circuit boards obtained bythe method of the eighth claim can be laminated further. Also, aplurality of just the circuit boards obtained by the method of theseventh claim may be laminated, a plurality of just the circuit boardsobtained by the method of the eighth claim may be laminated, or a singleor a plurality of circuit boards obtained by the method of eighth claimmay be laminated on just one surface of a circuit board obtained by theseventh claim.

(g)Multilayer Wiring Board

The arrangement and manufacturing method of the multilayer wiring boarddisclosed in the tenth to fifteen claim shall now be described.

(g-1) Arrangement

FIG. 3 is an explanatory sectional view, which shows the arrangement ofan example of a multilayer wiring board of the invention. The multilayerwiring board has a core wiring substrate 10, and with the core wiringsubstrate 10, a first substrate wiring layer 12 is formed on the uppersurface of an insulating substrate 11, a second substrate wiring layer13 is formed on the lower surface of insulating substrate 11, and thefirst substrate wiring layer 12 and second substrate wiring layer 13 areelectrically connected to each other via substrate shorting parts 14that extend through insulating substrate 11 in its thickness direction.

An upper insulating layer 20 is formed on the upper surface of corewiring substrate 10, an upper wiring layer 21 is formed on the uppersurface of upper insulating layer 20, and the upper wiring layer 21 iselectrically connected to first substrate wiring layer 12 via interlayershorting parts 22 that extend through upper insulating layer 20 in itsthickness direction. A solder resist layer 25, which has openings 26that expose lands for connection of parts on upper wiring layer 21, isprovided on the upper surface of upper insulating layer 20, whichincludes upper wiring layer 21.

Meanwhile, a lower insulating layer 30 is formed on the lower surface ofcore wiring substrate 10, a lower wiring layer 31 is formed on the lowersurface of lower insulating layer 30, and the lower wiring layer 31 iselectrically connected to second substrate wiring layer 13 viainterlayer shorting parts 32 that extend through lower insulating layer30 in its thickness direction. A solder resist layer 35, which hasopenings 36 that expose lands for connection of parts on lower wiringlayer 31, is provided on the upper surface of lower insulating layer 30,which includes lower wiring layer 31.

An insulating resin material of high heat resistance is preferably usedas the material that comprises the insulating substrate 11 of corewiring substrate 10. Specific examples include glass fiber reinforcedepoxy resins, glass fiber reinforced polyimide resins, glass fiberreinforced phenol resins, glass fiber reinforced bismaleimide triazineresins, polyimide resins, polyamide resins, polyester resins and thelike.

As substrate shorting parts 14, though shorting parts of variousarrangements used in prior-art printed wiring boards, such as shortingparts comprised of cylindrical metal deposits formed by electrolessdeposition or electroplating, shorting parts comprised of curedconductive paste material, with which conductive particles are dispersedin a thermosetting resin material and the like may be used, it ispreferable to use shorting parts, which are comprised of the materialthat comprises interlayer shorting parts 22 and interlayer shortingparts 32 to be described below, in other words, shorting parts comprisedof conductors formed by electrodeposition in an electrodepositionsolution, with which conductive microparticles and organicmicroparticles, which are comprised of at least one of either apolymerizable compound or a polymer, are dispersed in an aqueous medium.

Various thermosetting resin materials and radiation-curing resinmaterials used in prior-art printed wiring boards may be used as thematerial that comprises the upper insulating layer 20 and the lowerinsulating layer 30.

The interlayer shorting parts 22 and 32 formed in upper insulating layer20 and lower insulating layer 30 are comprised of conductors, with whichconductive microparticles are contained in a polymer substance, andthese conductors are formed by electrodeposition in a specificelectrodeposition solution.

The specific electrodeposition solution for forming interlayer shortingparts 22 and 32, is that conductive microparticles and organic particleswhich are comprised of at least one of either a polymerizable compoundor a polymer are dispersed in an aqueous medium. An aqueous dispersionforming conductive layer as set forth in any of the first to thirdclaims is especially preferable for use as the electrodepositionsolution.

Such interlayer shorting parts 22 and 32 contain conductivemicroparticles at an amount as volume percentage of preferably 40 to 99%and more preferably 60 to 95%.

By satisfying the above conditions, interlayer shorting parts 22 and 23,with a high conductivity, that is for example, with a volume resistivityof preferably 1×10⁻⁴Ω or less and more preferably 0.5×10⁻⁴Ω or less, canbe formed without fail.

(g-2) Manufacturing Method

An above-described multilayer wiring board can be manufactured forexample in the following manner.

First, as shown in FIG. 4, a core wiring substrate member 10A isprepared with which a first substrate wiring layer 12 is formed on theupper surface of an insulating substrate 11 and a metal layer 13A, whichis electrically connected to first substrate wiring layer 12 bysubstrate shorting parts 14, is formed on the lower surface ofinsulating substrate 11.

The core wiring substrate member 10A may be manufactured for example asfollows. That is, as shown in FIG. 5, a laminated material 10B, withwhich a metal layer 13A is formed on the lower surface of an insulatingsubstrate 11, is prepared, and as shown in FIG. 6, through holes 14H,which pass through the insulating substrate 11 in the thicknessdirection in correspondence to the substrate shorting parts to beformed, are formed on insulating substrate 11 of laminated material 10B.Electrodeposition is then performed on the laminating material 10B usingmetal layer 13A as the deposition cathode electrode in theabove-described electrodeposition solution to deposit the conductivemicroparticles and organic particles in the electrodeposition solutionand thereby form a deposit on the surface of metal layer 13A in theinteriors of through holes 14H. By then performing heating treatment ofthe deposit as necessary, substrate shorting parts 14, which extendthrough the insulating substrate 11 in its thickness direction, areformed as shown in FIG. 7. By then performing polishing of the uppersurface of insulating substrate 11 as necessary and thereafter formingfirst substrate wiring layer 12 on the upper surface of insulatingsubstrate 11, the core wiring substrate member 10A shown in FIG. 4 isobtained.

In the above, the method of illuminating laser light is favorably usedas the method of forming the through holes 14H in insulating substrate11 since through holes 14H of small diameter can thereby be obtained.

The constant voltage method is preferably used as the electrodepositionmethod since the thickness can then be controlled readily. The specificconditions for electrodeposition are set appropriately in considerationof the materials, concentrations and the like of the conductivemicroparticles and organic particles contained in the electrodepositionsolution and, for example, are an applied voltage of 50 to 500V and atreatment time of 0.5 to 200 minutes.

In the case where the deposit formed by electrodeposition is to be heattreated, the conditions of the heat treatment are set appropriately inconsideration of the materials and the like of the organic particlescontained in the electrodeposition solution and, for example, theheating temperature is preferably 100 to 400° C. and more preferably 150to 300° C. and the heating duration is preferably 5 minutes or more andmore preferably 10 minutes or more.

A wiring layer forming method that is used in the manufacture ofprior-art printed wiring boards may be used as the method of formingfirst substrate wiring layer 12. For example, the subtractive method, inwhich electroless deposition or electrolytic copper plating is appliedon the entire upper surface of insulating substrate 11 to form a metallayer and a part of the metal layer is then removed by photoetching toform the wiring layer, the additive method, in which a wiring layercomprised of a patterned metal layer is directly formed by performingphotolithography or electroless deposition on the upper surface ofinsulating substrate 11, and other methods may be used.

As shown in FIG. 8, an upper insulating layer 20, in which are formedthrough holes 22H corresponding to the interlayer shorting parts 22 thatare to be formed, is formed on the upper surface of such a core wiringsubstrate member 10A. Next, electrodeposition in an above-describedelectrodeposition solution is performed using first substrate wiringlayer 12 as the deposition cathode electrode to cause the conductivemicroparticles and the organic particles in the electrodepositionsolution to deposit and deposits are thereby formed on the surfaces offirst substrate wiring layer 12 inside through holes 22H. By thenperforming heat treatment of these deposits as necessary, interlayershorting parts 22, which extend through upper insulating layer 20 in itsthickness direction, are formed as shown in FIG. 9.

As the method of forming the upper insulating layer 20, having throughholes 22H formed therein, for the above process, the method of coating aliquid radiation-curing resin material onto the upper surface of corewiring substrate member 10A and then performing exposure treatment anddevelopment treatment on the coated film to form upper insulating layer20, in which through holes 22H are formed, the method of coating aliquid thermosetting resin material onto or setting a sheet-likethermosetting resin material on the surface of core wiring substrate10A, then performing heat treatment to form upper insulating layer 20,and then illuminating upper insulating layer 20 with laser to formthrough holes 22H may be used.

The method and specific conditions for electrodeposition are the same asthose for the above-described formation of substrate shorting parts 14.

After thus forming upper insulating layer 20 and interlayer shortingparts 22 and performing polishing treatment of the surface of upperinsulating layer 20 as necessary, electroless deposition orelectroplating is applied to the upper surface of upper insulating layer20 to form a metal layer 21A as shown in FIG. 10.

Photoetching is then performed on the metal layer 13A on core wiringsubstrate member 10A and a part of the metal layer 13A is therebyeliminated to form a second substrate wiring layer 13 on the lowersurface of insulating substrate 10. Core wiring substrate 10 is thusformed.

Then as shown in FIG. 12, a lower insulating layer 30, in which areformed through holes 32H corresponding to the interlayer shorting parts32 that are to be formed, is formed on the lower surface of core wiringsubstrate 10. Next, electrodeposition in an above-describedelectrodeposition solution is performed using second substrate wiringlayer 13 as the deposition cathode electrode to cause the conductivemicroparticles and the organic particles in the electrodepositionsolution to deposit and deposits are thereby formed on the surfaces ofsecond substrate wiring layer 13 inside through holes 32H. By thenperforming heat treatment of these deposits as necessary, interlayershorting parts 22, which extend through upper insulating layer 20 in itsthickness direction, are formed as shown in FIG. 13.

For the above, the method of forming the lower insulating layer 30, inwhich through holes 32H are formed, and the method and specificconditions of electrodeposition are the same as those described abovefor the formation of lower insulating layer 20 and interlayer shortingparts 22.

Photoetching is then performed on the metal layer 21A formed on thesurface of upper insulating layer 20 and a part of the metal layer 21Ais thereby eliminated to form an upper wiring layer 21 and a lowerwiring layer 31 is formed on the lower surface of lower insulating layer30 upon performing polishing treatment on the lower surface of the lowerinsulating layer 30 as necessary.

As the above-described method for forming the first substrate wiringlayer 12, a wire layer forming method used in the manufacture ofprior-art printed wiring boards may be used as a method of forming thelower wiring layer 31, and in the case where the subtractive method isto be used, the photoetching treatment may be carried out by the sameprocess as that of the photoetching treatment of metal layer 21A in theforming of upper wiring layer 21.

By then forming solder resist layers 25 and 35, having openings 26 and36 that expose the lands for connection of parts on upper wiring layer21 and lower wiring layer 31, on the upper surface of upper insulatinglayer 20, including the upper wiring layer 21, and the lower surface oflower insulating layer 30, including the lower wiring layer 31,respectively, a multilayer wiring board of the arrangement shown in FIG.3 can be obtained.

With such a multilayer wiring board, since interlayer shorting parts 22and 32 can be formed in a short time by electrodeposition usingsubstrate wiring layers 12 and 13 as deposition cathode electrodes in anelectrodeposition solution in which conductive microparticles andorganic particles are dispersed, high productivity is achieved in themanufacture of the multilayer wiring board.

Also, an electrodeposition solution of low viscosity can be preparedreadily, and by using such an electrodeposition solution, theelectrodeposition solution can be made to enter adequately into throughholes 21H and 31H, formed in upper insulating layer 20 and lowerinsulating layer 30, respectively, even when the diameters of throughholes 21H and 31H are small. As a result, the desired interlayershorting parts 22 and 32 can be formed without fail and a highconnection reliability can be obtained.

Since an aqueous dispersion forming conductive layer of the inventionenables the formation of a conductive layer by electrodeposition, aconductive layer of high precision in terms of film thickness, positionand the like can be formed readily in comparison to prior arts based oncoating, printing and the like. Also, since a film is formed not byplating but by electrodeposition of microparticles, the rate of growthof the film is high and the productivity is good. In the case using theaqueous dispersion, since organic particles, which are resin components,are electrodeposited along with conductive microparticles, a conductivelayer that excels in adhesive property to the substrate can be obtained.Since the resin component is dispersed as particles in an aqueous mediumin the invention, unlike the case where a resin component is used in anorganic solvent solution or in a non-solvent condition, the viscosity ofthe dispersive solution is little affected by the concentration andmolecular weight of the resin component and the dispersive solution canthus be made one with a viscosity that is suitable forelectrodeposition.

A conductive layer of the invention, which is formed using anabove-described aqueous dispersion, is, as has been mentioned above,excellent in adhesive property to the substrate and can be made high infilm thickness precision, positional precision or the like. By makinguse of these characteristics, a conductive layer of the invention can beapplied favorably to conductive circuits, bumps, circuit boards thatcombine such components, and other electronic parts.

According to a circuit board manufacturing method of the invention. acircuit board, which is formed from an aqueous dispersion of theinvention and is equipped with a conductive layer that includesconducting through parts that pass through the insulating layer, can bemanufactured efficiently.

According to the multilayer wiring board of the invention, sinceinterlayer shorting parts are formed in a short time byelectrodeposition using a substrate wiring layer as the depositionelectrode in an electrodeposition solution in which conductivemicroparticles and organic particles are dispersed, high productivitycan be achieved in the manufacture of the multilayer wiring board.

Also, an electrodeposition solution of low viscosity can be preparedreadily, and by using such an electrodeposition solution, theelectrodeposition solution can be made to enter adequately into throughholes that are formed in an insulating layer even when the diameters ofthe through holes are small. As a result, the desired interlayershorting parts can be formed inout fail and a high connectionreliability can be obtained.

According to a multilayer wiring board manufacturing method of theinvention, since interlayer shorting parts are formed in a short time byelectrodeposition using a substrate wiring layer as the depositionelectrode in an electrodeposition solution in which conductivemicroparticles and organic particles are dispersed, high productivitycan be achieved.

Also, an electrodeposition solution of low viscosity can be preparedreadily, and by using such an electrodeposition solution, theelectrodeposition solution can be made to enter adequately into throughholes that are formed in an insulating layer even when the diameters ofthe through holes are small. As a result, the desired interlayershorting parts can be formed inout fail and a multilayer wiring board ofhigh connection reliability can be manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) through (e) are schematic sectional views, which show theprocess of manufacturing a circuit board using Method 1.

FIGS. 2(a) through (e) are schematic sectional views, which show theprocess of manufacturing a circuit board using Method 2.

FIG. 3 is an explanatory sectional view, which shows the arrangement ofan example of a multilayer wiring board of the invention.

FIG. 4 is an explanatory sectional view, which shows a core wiringsubstrate member for obtaining the multilayer wiring board shown in FIG.3.

FIG. 5 is an explanatory sectional view, which shows a laminatedmaterial for obtaining the core wiring substrate member shown in FIG. 4.

FIG. 6 is an explanatory sectional view, which shows the condition wherethrough holes have been formed in the laminated material.

FIG. 7 is an explanatory sectional view, which shows the condition wheresubstrate shorting parts have been formed in an insulating substrate.

FIG. 8 is an explanatory sectional view, which shows the condition wherean upper insulating layer has been formed on the upper surface of thecore wiring substrate member.

FIG. 9 is an explanatory sectional view, which shows the condition whereinterlayer shorting parts have been formed in the upper insulatinglayer.

FIG. 10 is an explanatory sectional view, which shows the conditionwhere a metal layer has been formed on the upper surface of the upperinsulating layer.

FIG. 11 is an explanatory sectional view, which shows the conditionwhere a second substrate wiring layer has been formed on the lowersurface of the insulating substrate, thereby forming a core wiringsubstrate.

FIG. 12 is an explanatory sectional view, which shows the conditionwhere a lower insulating layer has been formed on the lower surface ofthe core wiring substrate.

FIG. 13 is an explanatory sectional view, which shows the conditionwhere interlayer shorting parts have been formed on the lower insulatinglayer.

FIG. 14 is an explanatory sectional view, which shows the conditionwhere an upper wiring layer has been formed on the surface of the upperinsulating layer and a lower wiring layer has been formed on the lowersurface of the lower insulating layer.

PREFERRED EMBODIMENTS OF THE INVENTION

The invention shall now be explained in more detail by way of examplesand comparative examples. Unless otherwise noted, the “parts” and “%” inthe following description are based on weight.

[1]Preparation of Conductive Microparticle Dispersive Solution SYNTHESISEXAMPLE 1 Copper Microparticle Dispersive Solution a

20 parts of copper microparticles, produced by the gas phasevaporization method (made by Vacuum Metallurgical Co., Ltd.;number-average primary particle diameter: 0.050 μm), and 80 parts ofisopropyl alcohol were mixed using a homomixer. 0.6 parts ofdiethanolamine were then added and ultrasonic dispersion was performedfor 10 minutes, thereby obtaining an alcohol dispersive solution ofcopper particles (solids concentration: 20%) inout any aggregates.

SYNTHESIS EXAMPLE 2 Copper Microparticle Dispersive Solution b

20 parts of copper microparticles, produced by the reduction method(made by Sumitomo Metal Industries Ltd.; number-average primary particlediameter: 0.3 μm), and 20 parts of isopropyl alcohol were mixed using ahomomixer. 1 part of monoethanolamine and 30 parts of isopropyl alcoholwere then added and the mixture was subject to a high-pressurehomogenizer (made by Hakusui Tech Co., Ltd.), thereby obtaining analcohol dispersive solution of copper particles (solids concentration:20%) inout any aggregates.

SYNTHESIS EXAMPLE 3 Copper Microparticle Dispersive Solution c

20 parts of copper microparticles, produced by the electrolysis method(made by Kawatetsu Kogyo Co., Ltd.; number-average primary particlediameter: 0.5 μm), and 30 parts of isopropyl alcohol were mixed using ahomomixer. 50 parts of isopropyl alcohol were then added and the mixturewas subject to a high-pressure homogenizer (made by Hakusui Tech Co.,Ltd.), thereby obtaining an alcohol dispersive solution of copperparticles (solids concentration: 20%) inout any aggregates.

SYNTHESIS EXAMPLE 4 Nickel Microparticle Dispersive Solution

10 parts of nickel microparticles, produced by the gas phasevaporization method (made by Vacuum Metallurgical Co., Ltd.;number-average primary particle diameter: 0.020 μm), and 90 parts ofisopropyl alcohol were mixed using a homomixer. 0.3 parts ofdiethanolamine were then added and ultrasonic dispersion was performedfor 10 minutes, thereby obtaining an alcohol dispersive solution ofnickel particles (solids concentration: 10%) inout any aggregates.

SYNTHESIS EXAMPLE 5 Silver Microparticle Dispersive Solution

20 parts of silver microparticles, produced by the gas phasevaporization method (made by Vacuum Metallurgical Co., Ltd.;number-average primary particle diameter: 0.050 μm), and 80 parts ofethyl alcohol were mixed using a homomixer. 0.3 parts of diethanolaminewere then added and ultrasonic dispersion was performed for 10 minutes,thereby obtaining an alcohol dispersive solution of silver particles(solids concentration: 20%) inout any aggregates.

[2]Preparation of Organic Particle Emulsion SYNTHESIS EXAMPLE 6Acrylic-based Resin Emulsion

100 parts of isopropyl alcohol were loaded into a reactor and heated to80° C. 85 parts of ethyl acrylate, 10 parts of methacrylic acid, 5 partsof glycidyl methacrylate and 1 part of azoisobutyronitrile were mixed ina separate container and then dripped continuously into the reactor overa duration of 5 hours to obtain an alcohol solution of acrylic resin. 20parts of the acrylic resin solution (10 parts as solids) and 0.2 partsof monoethanolamine were added while stirring strongly to 90 parts ofion-exchanged water, thereby obtaining an emulsion of anionic organicparticles, having an acrylic-based resin polymer as the principalcomponent.

SYNTHESIS EXAMPLE 7 Epoxy-based Resin Emulsion A

40 parts of a block isocyanate, comprised of tolylene diisocyanate and2-ethylhexanol, and 60 parts of an epoxy polycarboxylic acid adduct,obtained by reacting Epicoat 828 (made by Yuka Shell Epoxy Inc.) andpolycarboxylic acid (made by Johnson Polymer), were mixed and 3 parts ofmonoethanolamine were added as a pH adjuster. The mixture was thenloaded while stirring into 400 parts of ion-exchanged water, therebyobtaining an emulsion of anionic organic particles, having anepoxy-based resin precursor as the principal component.

SYNTHESIS EXAMPLE 8 Epoxy-based Resin Emulsion B

35 parts of a block isocyanate, comprised of tolylene diisocyanate and2-ethylhexanol, and 65 parts of an epoxy amine adduct, obtained byreacting Epicoat 828 (made by Yuka Shell Epoxy Inc.) and diethylamine,were mixed and 2.5 parts of acetic acid were added as a pH adjuster. Themixture was then loaded while stirring into 400 parts of ion-exchangedwater, thereby obtaining an emulsion of cationic organic particles,having an epoxy-based resin precursor as the principal component.

SYNTHESIS EXAMPLE 9 Polyimide-based Resin Emulsion

As tetracarboxylic dianhydrides, 32.29 g (90 millimoles) of3,3′,4,4′-biphenylsulfonetetracarboxylic dianhydride and 3.00 g (10millimoles) of1,3,3a,4,5,9b-hexahydro-5(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-c]-furan-1,3-dione,and, as diamine compounds, 36.95 g (90 millimoles) of2,2-bis[4-(4-aminophenoxy)phenyl]propane and 2.49 g (10 millimoles) oforganosiloxane (made by Shinetsu Chemicals Inc.; trade name: “LP7100”)were dissolved in 450 g of N-methyl-2-pyrrolidone and reacted at roomtemperature for 12 hours. Thereafter, 32 g of pyridine and 71 g ofacetic anhydride were added to the reaction solution and a dehydrationring-closing reaction was carried out for 3 hours at 100° C. Thereaction solution was then refined by distillation under reducedpressure, thereby obtaining a polyimide solution in a solids content of10%.

A reactor, in which 100 parts of y-butyrolactone were placed, was keptat 85° C. under a nitrogen gas atmosphere, and while continuously addinga mixed solution, comprised of 65 parts of n-butyl acrylate, 30 parts ofdimethylaminoethyl acrylate, 5 parts of glycidyl methacrylate, and 1part of azobisisobutyronitrile, into the reactor over a duration of 5hours, solution polymerization was carried out while stirring. After thecompletion of dripping, further stirring was continued at 85° C. for 2hours to complete the solution polymerization, thereby obtaining anacrylic polymer solution in a solids content of 50%.

50 parts (as solids) of the polyimide solution and 30 parts (as solids)of the acrylic polymer solution were mixed in 20 parts of Epicoat 828(trade name of product made by Yuka Shell Epoxy Inc.), and after lettingthe mixture react for 3 hours at 70° C., 3 parts of acetic acid wereadded and mixed gradually to adjust the pH- 1000 parts of distilledwater were then added gradually while stirring strongly, therebyobtaining an emulsion of cationic organic particles having apolyimide-based resin as the principal component.

[3]Preparation of Aqueous Dispersion EXAMPLE 1

500 parts (100 parts as solids) of the copper microparticle dispersivesolution a, obtained in Synthesis Example 1, and 100 parts (10 parts assolids) of the acrylic-based resin emulsion, obtained in SynthesisExample 6, were mixed to prepare an aqueous dispersion. The volume ratioof the copper microparticles to the acrylic-based resin contained in theaqueous dispersion was 53/47, and the water content as measured with theKarl Fischer method was 13% by weight.

EXAMPLE 2

500 parts (100 parts as solids) of the copper microparticle dispersivesolution b, obtained in Synthesis Example 2, and 100 parts (10 parts assolids) of the acrylic-based resin emulsion, obtained in SynthesisExample 6, were mixed to prepare an aqueous dispersion. The volume ratioof the copper microparticles to the acrylic-based resin contained in theaqueous dispersion was 53/47, and the water content as measured with theKarl Fischer method was 13% by weight.

EXAMPLE 3

1000 parts (100 parts as solids) of the nickel microparticle dispersivesolution, obtained in Synthesis Example 4, and 100 parts (10 parts assolids) of the acrylic-based resin emulsion, obtained in SynthesisExample 6, were mixed to prepare an aqueous dispersion. The volume ratioof the nickel microparticles to the acrylic-based resin contained in theaqueous dispersion was 53/47, and the water content as measured with theKarl Fischer method was 7% by weight.

EXAMPLE 4

500 parts (100 parts as solids) of the silver microparticle dispersivesolution, obtained in Synthesis Example 5, and 100 parts (10 parts assolids) of the acrylic-based resin emulsion, obtained in SynthesisExample 6, were mixed to prepare an aqueous dispersion. The volume ratioof the silver microparticles to the acrylic-based resin contained in theaqueous dispersion was 49/51, and the water content as measured with theKarl Fischer method was 13% by weight.

EXAMPLE 5

500 parts (100 parts as solids) of the silver microparticle dispersivesolution, obtained in Synthesis Example 5, and 50 parts (10 parts assolids) of the epoxy-based resin emulsion A, obtained in SynthesisExample 7, were mixed to prepare an aqueous dispersion. The volume ratioof the silver microparticles to the epoxy-based resin contained in theaqueous dispersion was 49/51, and the water content as measured with theKarl Fischer method was 7% by weight.

EXAMPLE 6

500 parts (100 parts as solids) of the copper microparticle dispersivesolution a, obtained in Synthesis Example 1, and 100 parts (10 parts assolids) of the epoxy-based resin emulsion B, obtained in SynthesisExample 8, were mixed to prepare an aqueous dispersion. The volume ratioof the copper microparticles to the epoxy-based resin contained in theaqueous dispersion was 53/47, and the water content as measured with theKarl Fischer method was 6.5% by weight.

EXAMPLE 7

500 parts (100 parts as solids) of the copper microparticle dispersivesolution c, obtained in Synthesis Example 3, and 30.1 parts (2.0 partsas solids) of the polyimide-based resin emulsion, obtained in SynthesisExample 9, were mixed to prepare an aqueous dispersion. The volume ratioof the copper microparticles to the polyimide-based resin contained inthe aqueous dispersion was 85/15, and the water content as measured withthe Karl Fischer method was 3.7% by weight.

EXAMPLE 8

1000 parts (100 parts as solids) of the nickel microparticle dispersivesolution, obtained in Synthesis Example 1, and 100 parts (10 parts assolids) of the epoxy-based resin emulsion B, obtained in SynthesisExample 8, were mixed to prepare an aqueous dispersion. The volume ratioof the nickel microparticles to the epoxy-based resin contained in theaqueous dispersion was 53/47, and the water content as measured with theKarl Fischer method was 3.5% by weight.

EXAMPLE 9

500 parts (100 parts as solids) of the silver microparticle dispersivesolution, obtained in Synthesis Example 5, and 100 parts (6.5 parts assolids) of the polyimide-based resin emulsion, obtained in SynthesisExample 9, were mixed to prepare an aqueous dispersion. The volume ratioof the silver microparticles to the polyimide-based resin contained inthe aqueous dispersion was 59/41, and the water content as measured withthe Karl Fischer method was 11% by weight.

COMPARATIVE EXAMPLE 1

In place of the 100 parts of the acrylic-based resin emulsion used inExample 1, 100 parts of ion-exchanged water were added to 500 parts (100parts as solids) of the copper microparticle dispersive solution a,obtained in Synthesis Example 1, to prepare an aqueous dispersion.

COMPARATIVE EXAMPLE 2

500 parts (100 parts as solids) of the alcohol dispersive solution a ofcopper microparticles, obtained in Synthesis Example 1, were useddirectly (that is, inout addition of an aqueous dispersion).

COMPARATIVE EXAMPLE 3

In place of the 100 parts of the epoxy-based resin emulsion used inExample 6, 500 parts of ion-exchanged water were added to 500 parts (100parts as solids) of the copper microparticle dispersive solution a,obtained in Synthesis Example 1, to prepare an aqueous dispersion.

[4]Formation and Performance Evaluation of Conductive Layers[4-1]Electrodeposition Onto Anode

Into each of the above-described dispersive solutions of Examples 1through 5 and Comparative Examples 1 and 2, a copper sputtered siliconwafer was placed as the anode and an SUS plate was placed as the counterelectrode (cathode). Particles were then electrodeposited onto the anodewith the constant voltage method at 70V (electrodeposition time: 2minutes). Thereafter, heating at 100° C. was performed for 10 minutesand further heating at 250° C. in a nitrogen atmosphere, in 3% hydrogenmixed in, was performed for 1 hour, thereby obtaining a conductive layerof 15 μm thickness. In the aqueous dispersion of Comparative Example 1,a film could not be obtained due to poor film forming property. Also inthe alcohol dispersive solution of Comparative Example 2, a film was notformed even when voltage was applied.

The preservation stability of each of the dispersive solutions ofExamples 1 through 5 and Comparative Examples 1 and 2 was evaluated bythe method described below. Also, the performance of each of theconductive layers obtained by electrodeposition was evaluated by themethods described below. The evaluation results are shown in Tables 1and 2.

Preservation Stability

A dispersive solution was placed in a plastic bottle and the dispersioncondition and viscosity after 10 days of storage at 20° C. were observedvisually. The evaluation results are indicated in the following twostages.

∘: There is no change in viscosity and the dispersion condition is good.

×: The dispersion separated into two layers.

Volume Resistivity

The volume resistivity was measured in compliance to JIS K6481.

Adhesive Property

Peeling tests using cellophane adhesive tape were performed and thepeeling of the conductive layer was evaluated in the following twostages.

∘: No changes whatsoever.

Δ: Slight changes were observed.

×: Peeling was observed.

TABLE 1 Example 1 Example 2 Example 3 Conductive Particle materialCopper Copper Nickel particles Volume resistivity¹⁾ 0.017 0.017 0.070Primary particle diameter (μm) 0.05 0.30 0.02 Parts (solids) 100 100 100Organic Particle material Acrylic Acrylic Acrylic particles Functionalgroup Carboxylic group Carboxylic group Carboxylic group Parts (solids)10 10 10 Aqueous Volume ratio²⁾ 53/47 53/47 53/47 dispersion pH 9.0 9.28.9 Viscosity (mPa · s) 10 10 10 Water content (%) 13 13 7 Solidsconcentration (%) 18 18 18 Preservation stability ∘ ∘ ∘ Conductive Filmthickness (μm) 15 16 15 layer Volume resistivity¹⁾ 1.2 0.08 0.9 Adhesiveproperty ∘ ∘ ∘ ¹⁾The unit of volume resistivity is (10⁻⁴Ω · cm). ²⁾Thevolume ratio is expressed as conductive particles/organic particles.

TABLE 2 Comparative Comparative Example 4 Example 5 Example 1 Example 2Conductive Particle material Silver Silver Copper Copper particlesVolume resistivity¹⁾ 0.016 0.016 0.017 0.017 Primary particle diameter(μm) 0.07 0.07 0.05 0.05 Parts (solids) 100 100 100 100 Organic Particlematerial Acrylic Epoxy — — particles Functional group Carboxylic groupCarboxylic group — — Parts (solids) 10 10 — — Aqueous Volume ratio²⁾49/51 49/51 100/0 100/0 dispersion pH 9.0 9.2 90 — Viscosity (mPa · s)10 10 10 7 Water content (%) 13 7 17 1 Solids concentration (%) 18 18 1720 Preservation stability ∘ ∘ x x Conductive Film thickness (μm) 15 15 —— layer Volume resistivity¹⁾ 0.1 0.2 — — Adhesive property ∘ ∘ — — ¹⁾Theunit of volume resistivity is (10⁻⁴Ω · cm). ²⁾The volume ratio isexpressed as conductive particles/organic particles.

As is clear from Tables 1 and 2, all of the aqueous dispersive solutionsof Examples 1 through 5 were excellent in preservation stability and theconductive layers formed by electrodeposition in these aqueousdispersions were low in volume resistivity and good in adhesive propertyto the substrate.

Meanwhile, in Comparative Example 1, which is of an aqueous dispersionthat does not contain organic particles, the film forming property wasinadequate, and in Comparative Example 2, which is of an alcoholdispersive solution that does not contain organic particles,electrodeposition could not be achieved. Also, the dispersive solutionsof Comparative Examples 1 and 2 were both poor in storage stability.

[4-2]Electrodeposition Onto Cathode

Into each of the above-described dispersive solutions of Examples 6through 9 and Comparative Examples 2 and 3, a copper sputtered siliconwafer was placed as the cathode and an SUS plate was placed as thecounter electrode (anode). Particles were then electrodeposited onto thecathode by the constant voltage method at 200V (electrodeposition time:2 minutes). Thereafter, heating at 100° C. was performed for 10 minutesand further heating at 250° C. in a nitrogen atmosphere, in 3% hydrogenmixed in, was performed for 1 hour, thereby obtaining a conductive layerof 15 μm thickness. In the aqueous dispersions of Comparative Examples 2and 3, a film did not form even upon electrodeposition.

The preservation stability of each of the dispersive solutions ofExamples 6 through 9 and Comparative Examples 2 and 3 was evaluated bythe method described above. Also, the performance of each of theconductive layers obtained by electrodeposition was evaluated by themethods described above. The evaluation results are shown in Tables 3and 4.

TABLE 3 Example 6 Example 7 Example 8 Conductive Particle materialCopper Copper Nickel particles Primary particle diameter (μm) 0.05 0.50.02 Parts (solids) 100 100 100 Organic Particle material EpoxyPolyimide Epoxy particles Parts (solids) 10 10 10 Aqueous Volume ratio53/47 85/15 53/47 dispersion (conductive particles/organic particles) pH9.0 5.5 8.9 Viscosity (mPa · s) 10 10 10 Water content (%) 6.5 11 3.5Solids concentration (%) 18 18 18 Preservation stability ∘ ∘ ∘Conductive Film thickness (μm) 15 16 15 layer Volume resistivity (10⁻⁴Ω· cm) 0.1 0.1 0.2 Adhesive property ∘ ∘ ∘

TABLE 4 Comparative Comparative Example 9 Example 2 Example 3 ConductiveParticle material Silver Copper Copper particles Primary particlediameter (μm) 0.07 0.05 0.05 Parts (solids) 100 100 100 Organic Particlematerial Polyimide — — particles Parts (solids) 6.5 — — Aqueous Volumeratio 59/41 100/0 100/0 dispersion (conductive particles/organicparticles) pH 9.0 — 9.0 Viscosity (mPa · s) 10 7 10 Water content (%) 111 56 Solids concentration (%) 18 20 17 Preservation stability ∘ x ∘Conductive Film thickness (μm) 15 Film could Film could layer not beformed. not be formed. Volume resistivity (10⁻⁴Ω · cm) 0.05 — — Adhesiveproperty ∘ — —

As is clear from Tables 3 and 4, all of the aqueous dispersive solutionsof Examples 6 through 9 were excellent in preservation stability and theconductive layers formed by electrodeposition in these aqueousdispersions were good in electrical characteristics and adhesiveproperty. Meanwhile, the aqueous dispersions of Comparative Examples 2and 3, which did not contain organic particles, did not have filmforming properties and the dispersion of Comparative Example 2 was poorin storage stability.

[5]Manufacture and Performance Evaluation of Circuit Boards

Circuit boards were manufactured using the prepared aqueous dispersionsand were evaluated in terms of performance.

EXAMPLE 10 Manufacture of Circuit Board by Method 1

A substrate of 100 μm thickness, prepared by impregnating BT Resin(trade name of product made by Mitsubishi Gas Chemicals Inc.) in glassfiber and semi-curing the resin, was used as a core insulating layer 41.Through holes 411 of 80 μm diameter were formed by carbon dioxide gaslaser processing at prescribed positions of the core insulating layer 41[FIG. 1(a)]. Next, a conductive foil 42, comprised of a copper foil of18 μm thickness, was adhered by heat pressing onto one of the surfacesof core insulating layer 41 [FIG. 1(b)].

The core insulating layer 41 in conductive foil 42 was then immersed inthe dispersion of Example 6, and using the conductive foil 42 as thecathode and the counter electrode as the anode, electrodeposition wasperformed while stirring at a temperature of 20° C. for 2 minutes at avoltage of 200V and a distance between electrodes of 15 cm. Theepoxy-based resin that was electrodeposited onto the interiors ofthrough holes 411 was then pre-dried at 100° C. for 15 minutes, therebyforming conducting through parts 421 [FIG. 1(c)].

A conductive foil was positioned and laminated onto the semi-curedsubstrate in conductive foil, and the substrate was cured completely byheating by a vacuum heat press for 1 hour at 200° C. in a nitrogenatmosphere, having 3% hydrogen mixed in, thereby obtaining a substratein which the interlayer circuits are connected by conducting throughparts 421 [FIG. 1(d)]. After then forming a pattern using a dry filmresist on conductive foil 42, etching was performed by immersion in aferric chloride etching solution, thereby obtaining a cured substrate ina circuit [FIG. 1(e)].

EXAMPLE 11 Manufacture of Circuit Board by Method 2

Using the substrate, on which a circuit was manufactured in Example 10,as the core wiring substrate 48 [FIG. 2(a)], a photosensitive epoxyresin was coated to a thickness of 100 μm onto both surfaces of corewiring substrate 48 to form insulating layers 45 [FIG. 2(b)].Thereafter, through holes 451 of 80 μm diameter were formed in apatterned manner in insulating layers 45, thereby forming insulatinglayer patterns 46 [FIG. 2(c)]. After then performing electrolessdeposition on the insulating layer patterns 46 [FIG. 2(d)], thesubstrate was immersed in the dispersion of Example 7, and usingelectroless plated layers 47 as the cathode and the counter electrode asthe anode, electrodeposition was performed while stirring at 20° C., adistance between electrodes of 15 cm, and a voltage of 200V. Theelectrodeposited polyimide-based resin was then pre-dried for 15 minutesat 100° C., thereby forming conductive layers 43 over the entiresurfaces of electroless plated layers 47 [FIG. 2(e)]. Parts of theseconductive layers 43 are conducting through parts 432 formed in theinteriors of through holes 451. Further heating for 1 hour at 230° C.under a nitrogen atmosphere, having 3% hydrogen mixed in, was thenperformed in a heat drying oven to completely cure the conductinglayers, thereby obtaining a circuit board, in which interlayer circuitsare joined by conducting through parts 432.

EXAMPLE 12

In forming the conducting through parts 421 of Example 10,electrodeposition was performed using the dispersive solution of Example7 and pre-drying was performed for 15 minutes at 100° C. The substratewas thereafter immersed in a copper electroplating solution (trade name:“Microfab Cu 200”; made by Nihon Electroplating Inc.) and usingconductive foil 42 as the cathode, electrodeposition was performed for 5minutes at a voltage of IV and a conduction time during 1 cycle of 100ms (0V for 500 ms). Otherwise, a cured substrate in circuit was obtainedin the same manner as in Example 10.

COMPARATIVE EXAMPLE 4

Unlike Example 10, in which conducting through parts 421 in theinteriors of through holes 411 were formed by electrodeposition, acopper-based conductive paste (viscosity: 100 Pa·s) were filled intothrough holes 411 via a metal plate (thickness: 100 μm; hole diameter:90 μm) and by means of a screen printer. Otherwise, the circuit board ofComparative Example 4 was obtained in the same manner as in Example 10.

The circuit boards that were obtained were evaluated as described below.The results are shown in table 5

Resistivity of Insulating Layer

The resistivity of the insulating layer was measured in compliance toJIS K6911.

Resistivity of Conducting Through Parts

The volume resistivity was determined by measuring the resistivityacross the upper and lower layers.

Connection Reliability Test of Conducting Through Parts

The cycle of leaving a circuit board for 30 minutes at −55° C. and thenfor 30 minutes at 125° C. was repeated 500 times and the change of theelectrical resistance was examined in a circuit to which 500 bumps wereconnected. The test result was indicated as passing (∘) if theelectrical resistance was less than 250 mΩ and as failing (×) if theelectrical resistance was 250 mΩ or more.

Solder Dipping Test

The electrical resistance was examined in a circuit to which 500 bumpswere connected before and after immersion of the circuit board for 10seconds in a bath of molten solder heated at 260° C. In regard to thetest results, since if the electrical resistance is less than 250 mΩ,the resistance per bump will be less than 0.5 mΩ, the condition wasregarded as passing (∘) and if the electrical resistance was 250 mΩ ormore, the condition was regarded as failing (×).

TABLE 5 Comparative Example 10 Example 11 Example 12 Example 4 Formingmaterial of Dispersive Dispersive Dispersive Commercially soldconducting through parts solution of solution of solution of conductivepast Example 6 Example 7 Example 7 Circuit board Method 1 Method 2Method 1 Printing manufacturing method (electrodeposition)(electrodeposition) (electrodeposition) Resistivity of conducting 0.20.3 0.1 10 through parts (mΩ · cm) Connection reliability of conductingthrough parts Temperature cycle test ∘ ∘ ∘ x Solder dipping test ∘ ∘ ∘ x

As can be understood from Table 5, in the circuit boards equipped in theconductive layer formed from an aqueous dispersion of the invention, theinterlayer circuits were connected at a low resistivity by theconducting through parts and the connection reliability was alsoexcellent. On the other hand, in Comparative Example 4, in whichconducting through parts were formed by the printing method using aprior-art conductive paste, since the interiors of the through holes of80 μm diameter could not be filled inout fail by the highly viscousconductive paste, the resistivity of the conducting through parts washigh and the connection reliability was inadequate.

[6]Manufacture and Performance Evaluation of Multilayer Wiring BoardsEXAMPLE 13 (1)Preparation of Core Wiring Substrate Member

First, a laminated material, in which a copper layer of 18 μm thicknesswas formed on an insulating substrate comprised of a glass fiberreinforced epoxy resin of 500 μm thickness, was prepared, and throughholes of 100 μm diameter were formed in the insulating substrate of thelaminated material by a carbon dioxide gas laser device (see FIGS. 5 and6).

The laminated material was then immersed, in one surface of the metallayer thereof being protected, in the dispersion of Example 6, and usingthe metal layer as the deposition cathode electrode, electrodepositionby the constant voltage method was performed in the conditions of anelectrodeposition solution temperature of 20° C., a distance betweenelectrodes of 25 cm, an application voltage of 200V, and a treatmenttime of 60 minutes to form a deposit of conductive microparticles andorganic particles in the through holes of the insulating substrate.After then pre-drying at 100° C. for 15 minutes, heating was performedat 170° C. for 30 minutes in a reducing atmosphere (in nitrogen gascontaining 3% hydrogen) to form substrate shorting parts (see FIG. 7).

After then polishing the surface of the insulating substrate of thelaminated material, electroless copper plating and electrolytic copperplating were applied to the surface of the insulating substrate to forma metal layer of 20 μm thickness, and by performing photoetching on themetal layer, a first substrate wiring layer was formed, therebymanufacturing a core wiring substrate member, having a first substratewiring layer and having a metal layer at the lower surface that iselectrically connected via the substrate shorting parts to the firstsubstrate wiring (see FIG. 4).

(2)Formation of Upper Insulating Layer, Interlayer Shorting Parts, andCore Wiring Substrate

An epoxy resin prepreg sheet of 60 μm thickness was heat pressed at atemperature of 165° C. and a pressure of 30 kg/cm² onto the uppersurface of the core wiring substrate obtained in the above-describedprocess of (1) to form an upper insulating layer, and through holes of100 μm diameter were formed on the upper insulating layer by means of acarbon dioxide gas laser device (see FIG. 8).

Then in the lower surface of the metal layer of the core wiringsubstrate member being protected, electrodeposition by the constantvoltage method was performed in the dispersion of Example 6, using thefirst substrate wiring layer as the deposition cathode, and in theconditions of an electrodeposited solution temperature of 20° C., adistance between electrodes of 25 cm, an application voltage of 200V,and a treatment time of 15 minutes to form a deposit of conductivemicroparticles and organic particles in the through holes of the upperinsulating layer. After then pre-drying at 100° C. for 15 minutes,heating was performed at 170° C. for 30 minutes in a reducing atmosphere(in nitrogen gas containing 3% hydrogen) to form interlayer shortingparts (see FIG. 9).

After then polishing the surface of the upper insulating layer,electroless copper plating and electrolytic copper plating were appliedto the surface of the upper insulating layer to form a metal layer of 20μm thickness (see FIG. 10), and by performing photoetching on the metallayer on the core wiring substrate member, a second substrate wiringlayer was formed, thereby manufacturing a core wiring substrate (seeFIG. 11).

(3)Formation of Lower Insulating Layer, Interlayer Shorting Parts, UpperWiring Layer, and Lower Wiring Layer

An epoxy resin prepreg sheet of 60 μm thickness was heat pressed at atemperature of 165° C. and a pressure of 30 kg/cm² onto the lowersurface of the core wiring substrate, obtained in the above-describedprocess of (2) and having an upper insulating layer and interlayershorting parts formed on the upper surface, thereby forming a lowerinsulating layer, and through holes of 100 μm diameter were formed onthe lower insulating layer by means of a carbon dioxide gas laser device(see FIG. 12).

Then in the upper surface of the metal layer formed on the upperinsulating layer being protected, electrodeposition by the constantvoltage method was performed in the dispersion of Example 6, using thesecond substrate wiring layer as the deposition cathode, and in theconditions of an electrodeposition solution temperature of 20° C., adistance between electrodes of 25 cm, an application voltage of 200V,and a treatment time of 8 minutes, thereby forming a deposit ofconductive microparticles and organic particles in the through holes ofthe upper insulating layer. After then pre-drying at 100° C. for 15minutes, heating was performed at 170° C. for 30 minutes in a reducingatmosphere (in nitrogen gas containing 3% hydrogen), thereby forminginterlayer shorting parts (see FIG. 13).

After then polishing the surface of the lower insulating layer,electroless copper plating and electrolytic copper plating were appliedto the surface of the lower insulating layer, thereby forming a metallayer of 20 μm thickness. By then performing photoetching on the metallayer formed on each of the surfaces of the upper insulating layer andlower insulating layer, an upper wiring layer and a lower wiring layerwere formed (see FIG. 14).

By then forming solder resist layers on the surface of the upperinsulating layer, including the upper wiring layer, and the surface ofthe lower insulating layer, including the lower wiring layer, amultilayer wiring board of the invention was manufactured.

In the above, the proportion as volume percentage of the conductivemicroparticles in the substrate shorting parts and the interlayershorting parts, formed on each of the upper insulating layer and thelower insulating layer, was approximately 53%.

EXAMPLE 14

The dispersion of Example 7 was used in place of the dispersion ofExample 6 in the forming of the substrate shorting parts and theinterlayer shorting parts, and after pre-drying of the deposit formed byelectrodeposition, immersion in a copper electroplating solution (tradename: “Microfab Cu 200”; made by Nihon Electroplating Inc.) andelectrodeposition using conductive foil 42 as the cathode was performedfor 5 minutes at a voltage of 1V and a conduction time during 1 cycle of100 ms (0V for 300 ms). Otherwise, a multilayer wiring board of theinvention was manufactured in the same manner as in Example 13.

In the above, the proportion as volume percentage of the conductivemicroparticles in the substrate shorting parts and the interlayershorting parts, formed on each of the upper insulating layer and thelower insulating layer, was approximately 85%.

COMPARATIVE EXAMPLE 5

Instead of forming the substrate shorting parts and the interlayershorting parts by use of an electrodeposition solution, the substrateshorting parts and interlayer shorting parts were formed by filling thethrough holes in a copper-based conductive paste (viscosity: 100 Pa·s)via a metal plate (thickness: 100 μm; hole diameter: 90 μm) and by meansof a screen printer and then performing heat treatment at 170° C. for 30minutes in a reducing atmosphere (in nitrogen gas containing 3%hydrogen). Otherwise, a multilayer wiring board for comparison wasmanufactured in the same manner as in Example 12.

Evaluation of the Multilayer Wiring Boards (1)Initial ElectricalResistance of the Wiring

The values of the electrical resistance across the connection lands ofthe upper wiring layer and the connection lands of the lower wiringlayer of a multilayer wiring board were measured and the average valuethereof was determined.

(2)Electrical Resistance of the Wiring After Heat Cycle Test

The cycle of leaving a multilayer wiring board for 30 minutes at −55° C.and then for 30 minutes at 125° C. was repeated 500 times in total, andthereafter, the values of the electrical resistance across theconnection lands of the upper wiring layer and the connection lands ofthe lower wiring layer of the multilayer wiring board were measured andthe average value per connection land was determined.

The results of the above are shown in Table 6.

TABLE 6 Electrical resistance (mΩ) Initial After heat cycle test Example13 0.2 0.3 Example 14 0.1 0.1 Comparative Example 5 0.4 1.0

As is clear from the results of Table 6, the multilayer wiring boards ofExample 13 and Example 14, were low in the electrical resistance of thewiring, small in the change of electrical resistance of the wiring afterthe heat cycle test, and where thus confirmed to be of high connectionreliability.

The invention is not limited to the embodiments described above andvarious modifications may be made. For example, the insulating layer tobe formed on the core wiring substrate may be made on either one surfaceor the other surface of the core wiring substrate and another insulatinglayer may be laminated on top of the insulating layer. Also, the corewiring substrate may have a multilayer arrangement as long as substratewiring layers that are mutually connected electrically are formed onboth surfaces.

What is claimed is:
 1. An aqueous dispersion forming conductive layercharacterized in that conductive microparticles, with a number-averageparticle diameter of 1 μm or less, and organic particles, which arecomprised of at least one of either a polymerizable compound or apolymer, are dispersed in an aqueous medium and in enabling theformation of a conductive layer by electrodeposition.
 2. An aqueousdispersion forming conductive layer as set forth in claim 1, wherein thevolume ratio of said conductive microparticles to said organic particlesis 99:1 to 40:60.
 3. An aqueous dispersion forming conductive layer asset forth in claim 1, which is prepared by mixing a conductivemicroparticle dispersive solution, in which said conductivemicroparticles are dispersed in an organic solvent, and an organicparticle dispersive solution, in which said organic particles aredispersed in an aqueous medium.
 4. An conductive layer characterized inbeing formed by electrodeposition using a aqueous dispersion formingconductive layer as set forth in claim 1 and in that the volumeresistivity is 10⁻⁴ Ω·cm or less.
 5. An electronic part characterized inbeing equipped in a conductive layer formed by electrodeposition usingan aqueous dispersion forming conductive layer as set forth in claim 1.6. A circuit board characterized in having an insulating layer and aconductive layer, which is formed by an electrodeposition method usingan aqueous dispersion forming conductive layer as set forth in claim 1as an electrodeposition solution and includes conducting through partsthat pass through said insulating layer.
 7. A circuit boardmanufacturing method characterized in using an aqueous dispersionforming conductive layer as set forth in claim 1 and being comprised of;(a) a process of forming through holes in an insulating layer, (b) aprocess of setting a conductive foil on a part of one surface of saidinsulating layer that includes the openings at one end of said throughholes, and (c) a process of forming conducting through parts inside saidthrough holes by an electrodeposition method using said aqueousdispersion forming conductive layer as the electrodeposition solutionand using said conductive foil as one of the electrodes.
 8. A circuitboard manufacturing method characterized in using an aqueous dispersionforming conductive layer as set forth in claim 1 and being comprised of;(a) a process of forming an insulating layer on a core wiring substrateon which a conducting pattern has been formed, (b) a process ofpatterning said insulating layer and forming an insulating layer patternin through holes that expose a part of said conducting pattern, (c) aprocess of forming an electroless plated layer at parts including theinteriors of said through holes by electroless deposition using saidinsulating layer pattern as a mask material, and (d) a process offorming a conductive layer, which includes conducting through parts atinteriors of said through holes, by electrodeposition using said aqueousdispersion forming conductive layer as an electrodeposition solution andusing said conducting pattern and said electrolessplated layer as one ofelectrodes.
 9. A circuit board manufacturing method characterized inthat a plurality of circuit boards, obtained by a method set forth inclaim 7, are laminated.
 10. A circuit board manufacturing methodcharacterized in that a plurality of circuit boards, obtained by amethod set forth in claim 8, are laminated.
 11. A multilayer wiringboard characterized in having a core wiring substrate, which is arrangedby forming substrate wiring layers that are mutually connectedelectrically on both surfaces of an insulating substrate, an insulatinglayer, which is laminated onto at least one surface of the core wiringsubstrate, a wiring layer, which is formed on said insulating layer, andinterlayer shorting parts, which extend through said insulating layer inthe thickness direction and electrically connect said wiring layer tosaid substrate wiring layer, said multilayer wiring board beingcharacterized in that each of said interlayer shorting parts iscomprised of a conductor, in which conductive microparticles arecontained inside a polymer substance, and in that said conductor isformed by electrodeposition in an electrodeposition solution, in whichconductive microparticles and organic particles, comprised of at leastone of either a polymerizable compound or a polymer, are dispersed in anaqueous medium.
 12. A multilayer wiring board as set forth in claim 11,wherein said core wiring substrate has substrate shorting parts, whichelectrically connect said substrate wiring layers, formed on both sidesof said insulating substrate, to each other and extend through saidinsulating substrate in the thickness direction, each of said substrateshorting parts is comprised of a conductor, in which conductivemicroparticles are contained inside a polymer substance, and saidconductor is formed by electrodeposition in an electrodepositionsolution, in which conductive microparticles and organic particles,comprised of at least one of either a polymerizable compound or apolymer, are dispersed in an aqueous medium.
 13. A multilayer wiringboard as set forth in claim 11, wherein the proportion as volumepercentage of said conductive microparticles in said conductors thatcomprise said interlayer shorting parts and/or substrate shorting partsis 40 to 99%.
 14. A method of manufacturing a multilayer wiring board asset forth in claim 11, characterized in being comprised of; a process ofpreparing a core wiring substrate member, which is comprised of aninsulating substrate, a substrate wiring layer, formed on one surface ofsaid insulating substrate, and a metal layer, formed on the othersurface of said insulating substrate and electrically connected to saidsubstrate wiring layer, a process of forming an insulating layer, havingthrough holes formed in correspondence to interlayer shorting parts tobe formed on the substrate wiring layer, on one surface of said corewiring substrate member, and a process of forming conductors thatcomprise said interlayer shorting parts inside said through holes ofsaid insulating layer by electrodeposition using an electrodepositionsolution, in which conductive microparticles and organic particlescomprised of at least one of either a polymerizable compound or apolymer, are dispersed in an aqueous medium, with said substrate wiringlayer of the core wire substrate member on which said insulating layerwas formed, as a deposition electrode.
 15. A multilayer wiring boardmanufacturing method as set forth in claim 14, wherein a substrateforming material, having an insulating substrate and a metal layer,formed on at least one surface of said insulating substrate, isprepared, through holes, which pass through said insulating substrate ofsaid substrate forming material in the thickness direction thereof, areformed, and after performing electrodeposition, using said metal layerof said substrate forming material as the deposition electrode, in anelectrodeposition solution, in which conductive microparticles andorganic particles comprised of at least one of either a polymerizablecompound or a polymer, are dispersed in an aqueous medium, to formconductors that comprise substrate shorting parts inside said throughholes of said insulating substrate, a substrate wiring part is formed onone surface of said insulating substrate to form said core wiringsubstrate member.
 16. A multilayer wiring board manufacturing method asset forth in claim 14, wherein the volume ratio of said conductivemicroparticles to said organic particles is 99:1 to 40:60.